Holographic display with a variable beam deflection

ABSTRACT

A holographic display including a spatial light modulator, and including a position detection and tracking system, such that a viewer&#39;s eye positions are tracked, with variable beam deflection to the viewer&#39;s eye positions being performed using a microprism array which enables controllable deflection of optical beams.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority of PCT/EP2008/056030, filed on May16, 2008, which claims priority to Great Britain Application No.0709376.8, filed May 16, 2007; Great Britain Application No. 0709379.2,filed May 16, 2007; German Application No. 10 2007 023 737.7, filed May16, 2007; German Application No. 10 2007 023 740.7, filed May 16, 2007;German Application No. 10 2007 023 785.7, filed May 16, 2007; GermanApplication No. 10 2007 023 739.3, filed May 16, 2007; Great BritainApplication No. 0718595.2, filed Sep. 25, 2007; Great BritainApplication No. 0718596.0, filed Sep. 25, 2007; Great BritainApplication No. 0718598.6, filed Sep. 25, 2007; Great BritainApplication No. 0718602.6, filed Sep. 25, 2007; Great BritainApplication No. 0718607.5, filed Sep. 25, 2007; Great BritainApplication No. 0718614.1, filed Sep. 25, 2007; Great BritainApplication No. 0718617.4, filed Sep. 25, 2007; Great BritainApplication No. 0718619.0, filed Sep. 25, 2007; Great BritainApplication No. 0718622.2, filed Sep. 25, 2007; Great BritainApplication No. 0718626.5, filed Sep. 25, 2007; Great BritainApplication No. 0718629.9, filed Sep. 25, 2007; Great BritainApplication No. 0718632.3, filed Sep. 25, 2007; Great BritainApplication No. 0718633.1, filed Sep. 25, 2007; Great BritainApplication No. 0718634.9, filed Sep. 25, 2007; Great BritainApplication No. 0718636.4, filed Sep. 25, 2007; Great BritainApplication No. 0718640.6, filed Sep. 25, 2007; Great BritainApplication No. 0718649.7, filed Sep. 25, 2007; Great BritainApplication No. 0718654.7, filed Sep. 25, 2007; Great BritainApplication No. 0718656.2, filed Sep. 25, 2007; and Great BritainApplication No. 0718659.6, filed Sep. 25, 2007, the entire contents ofwhich are hereby incorporated in total by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a holographic display, especially to aholographic display on which computer-generated video holograms (CGHs)are encoded on a spatial light modulator. The holographic display maygenerate three dimensional holographic reconstructions.

2. Technical Background

Computer-generated video holograms (CGHs) are encoded in one or morespatial light modulators (SLMs); the SLMs may include electrically oroptically controllable cells. The cells modulate the amplitude and/orphase of light by encoding hologram values corresponding to avideo-hologram. The CGH may be calculated e.g. by coherent ray tracing,by simulating the interference between light reflected by the scene anda reference wave, or by Fourier or Fresnel transforms. An ideal SLMwould be capable of representing arbitrary complex-valued numbers, i.e.of separately controlling the amplitude and the phase of an incominglight wave. However, a typical SLM controls only one property, eitheramplitude or phase, with the undesirable side effect of also affectingthe other property. There are different ways to modulate the light inamplitude or phase, e.g. electrically addressed liquid crystal SLM,optically addressed liquid crystal SLM, magneto optical SLM, micromirror devices or acousto-optic modulators. The modulation of the lightmay be spatially continuous or composed of individually addressablecells, one-dimensionally or two-dimensionally arranged, binary,multi-level or continuous.

In the present document, the term “encoding” denotes the way in whichregions of a spatial light modulator are supplied with control values toencode a hologram so that a 3D-scene can be reconstructed from the SLM.

In contrast to purely auto-stereoscopic displays, with video hologramsan observer sees an optical reconstruction of a light wave front of athree-dimensional scene. The 3D-scene is reconstructed in a space thatstretches between the eyes of an observer and the spatial lightmodulator (SLM). The SLM can also be encoded with video holograms suchthat the observer sees objects of a reconstructed three-dimensionalscene in front of the SLM and other objects on or behind the SLM.

The cells of the spatial light modulator are preferably transmissivecells which are passed through by light, the rays of which are capableof generating interference at least at a defined position and over acoherence length of a few millimetres or more. This allows holographicreconstruction with an adequate resolution in at least one dimension.This kind of light will be referred to as ‘sufficiently coherent light’.

In order to ensure sufficient temporal coherence, the spectrum of thelight emitted by the light source must be limited to an adequatelynarrow wavelength range, i.e. it must be near-monochromatic. Thespectral bandwidth of high-brightness light emitting diodes (LEDs) issufficiently narrow to ensure temporal coherence for holographicreconstruction. The diffraction angle at the SLM is proportional to thewavelength, which means that only a monochromatic source will lead to asharp reconstruction of object points. A broadened spectrum will lead tobroadened object points and smeared object reconstructions. The spectrumof a laser source can be regarded as monochromatic. The spectral linewidth of a LED is sufficiently narrow to facilitate goodreconstructions.

Spatial coherence relates to the lateral extent of the light source.Conventional light sources, like LEDs or Cold Cathode Fluorescent Lamps(CCFLs), can also meet these requirements if they radiate light throughan adequately narrow aperture. Light from a laser source can be regardedas emanating from a point source within diffraction limits and,depending on the modal purity, leads to a sharp reconstruction of theobject, i.e. each object point is reconstructed as a point withindiffraction limits.

Light from a spatially incoherent source is laterally extended andcauses a smearing of the reconstructed object. The amount of smearing isgiven by the broadened size of an object point reconstructed at a givenposition. In order to use a spatially incoherent source for hologramreconstruction, a trade-off has to be found between brightness andlimiting the lateral extent of the source with an aperture. The smallerthe light source, the better is its spatial coherence.

A line light source can be considered to be a point light source if seenfrom a right angle to its longitudinal extension. Light waves can thuspropagate coherently in that direction, but incoherently in all otherdirections.

In general, a hologram reconstructs a scene holographically by coherentsuperposition of waves in the horizontal and the vertical directions.Such a video hologram is called a full-parallax hologram. Thereconstructed object can be viewed with motion parallax in thehorizontal and the vertical directions, like a real object. However, alarge viewing angle requires high resolution in both the horizontal andthe vertical direction of the SLM.

Often, the requirements on the SLM are lessened by restriction to ahorizontal-parallax-only (HPO) hologram. The holographic reconstructiontakes place only in the horizontal direction, whereas there is noholographic reconstruction in the vertical direction. This results in areconstructed object with horizontal motion parallax. The perspectiveview does not change upon vertical motion. A HPO hologram requires lessresolution of the SLM in the vertical direction than a full-parallaxhologram. A vertical-parallax-only (VPO) hologram is also possible butuncommon. The holographic reconstruction occurs only in the verticaldirection and results in a reconstructed object with vertical motionparallax. There is no motion parallax in the horizontal direction. Thedifferent perspective views for the left eye and right eye have to becreated separately.

Real-time calculation of holograms requires great computationalperformance, which can be realised presently for example with the helpof expensive, specially made hardware with Field Programmable GateArrays (FPGAs), full custom ICs, or Application Specific IntegratedCircuits (ASICs), or by using multiple central processing units (CPUs)which are capable of parallel processing.

In thin film transistor (TFT) displays, the pixel pitch in orthogonaldirections determines the area per pixel. This area is divided into thetransparent electrode for liquid crystal (LC) control, the TFT togetherwith the capacitor and the column and row wires. The required frequencyon the column wires and the display dimensions define the requiredprofile and thus the width of the row and column wires.

Ideal holographic displays require a much higher resolution thancommercially available TFT-based monitor devices provide today. Thehigher the resolution, the smaller is the pixel pitch, while thefrequency on the row and column wires increases due to the higher numberof rows. This in turn causes the proportion of the area covered by rowand column wires of the entire pixel area to grow superproportionatelycompared with the increase in resolution. Consequently, there is muchless space available for the transparent electrode, so that thetransmittance of the display will drop significantly. This means thatideal high-resolution holographic displays with a high refresh rate canonly be produced with severe restrictions. Due to the extreme demandsmade on the computational performance, the hardware which can be usedtoday for real-time calculation of holograms is very expensive,irrespective of which particular type of hardware is used. Because ofthe great amount of data involved, the transfer of image data from thecomputing unit to the display is also very difficult.

A common construction of an active matrix liquid crystal display devicewill be briefly explained, with reference to prior art FIG. 10 takenfrom U.S. Pat. No. 6,153,893; U.S. Pat. No. 6,153,893 is incorporatedherein in its entirety by reference. As shown in FIG. 10, this activematrix display device has a flat panel structure comprising a mainsubstrate 101, an opposed substrate 102 and a space 103 affixing themain substrate to the opposed substrate, and liquid crystal material isheld between the two substrates. On the surface of the main substrateare formed a display part 106 consisting of pixel electrodes 104 andswitching devices 105 for driving the pixel electrodes 104 arranged in amatrix, and peripheral driving parts 107 connected to the display part106. The switching devices 105 consist of thin film transistors. Thinfilm transistors are also formed in the peripheral parts 107 as circuitelements.

Document WO 2006/066906 filed by the applicant, which is incorporated byreference, describes a method for computing computer-generated videoholograms. According to that method, objects with complex amplitudevalues of a three-dimensional scene are assigned to matrix dots ofparallel virtual section layers such that for each section layer anindividual object data set is defined with discrete amplitude values inmatrix dots, and a holographic encoding for a spatial light modulator ofa hologram display is computed from the image data sets.

According to publication WO 2008/025839 of the applicant, which isincorporated by reference, the following steps are carried out aided bya computer:

-   -   A diffraction image is computed in the form of a separate        two-dimensional distribution of wave fields for an observer        plane, which is situated at a finite distance and parallel to        the section layers, from each object data set of each        tomographic scene section, where the wave fields of all sections        are computed for at least one common virtual observer window        which is situated in the observer plane near the eyes of an        observer, the area of said observer window being reduced        compared with the video hologram;    -   The computed distributions of all section layers are added to        define an aggregated wave field for the observer window in a        data set which is referenced in relation to the observer plane;    -   The reference data set is transformed into a hologram plane,        which is situated at a finite distance and parallel to the        reference plane, so as to create a hologram data set for an        aggregated computer-generated hologram of the scene, where the        spatial light modulator is disposed in the hologram plane, and        where the scene is reconstructed in the space in front of the        observer eyes with the help of said spatial light modulator        after encoding.

The methods and displays mentioned above are based on the idea not toreconstruct the object of the scene itself, but to reconstruct in one ormultiple virtual observer windows the wave front which would be emittedby the object.

The observer can watch the scene through the virtual observer windows.The virtual observer windows cover the pupils of the observer eyes andcan be tracked to the actual observer position with the help of knownposition detection and tracking systems. A virtual, frustum-shapedreconstruction space stretches between the spatial light modulator ofthe hologram display and the observer windows, where the SLM representsthe base and the observer window the top of the frustum. If the observerwindows are very small, the frustum can be approximated as a pyramid.The observer looks though the virtual observer windows towards thedisplay and receives in the observer window the wave front whichrepresents the scene. Due to the large number of necessarytransformations, the holographic encoding process causes greatcomputational load. Real-time encoding would require costlyhigh-performance computing units.

Filing WO 2008/025839 of the applicant discloses a method which allowsone to generate video holograms from three-dimensional image data withdepth information in real time. This makes it possible to generate theseholograms using relatively simple and inexpensive computing units.

Filing WO 2008/025839 of the applicant discloses a method for generatingcomputer-generated video holograms in real time. Hologram values for therepresentation of a three-dimensional scene which is structured throughobject points on a spatial light modulator SLM are encoded based onimage data with depth information. In analogy with the prior artsolution mentioned above, the method disclosed in WO 2008/025839 isbased on the idea not to reconstruct the object of the scene itself, butto reconstruct in one or multiple virtual observer windows the wavefront which would be emitted by the object. A modulated wave field isgenerated from sufficiently coherent light by a spatial light modulatorSLM, which is controlled by hologram values, and the desired real orvirtual three-dimensional scene is reconstructed through interference inspace. Virtual observer windows are generated in frustum-shapedreconstruction spaces with the SLM as a base. The windows are situatednear the observer eyes and can be tracked to the actual observerposition with the help of known position detection and tracking systems.The method disclosed in WO 2008/025839 is based on the fact that theregion in which an observer sees a scene is defined by a frustum-shapedreconstruction space which stretches from the SLM to the observerwindow. The frustum can be approximated by a pyramid, because theobserver window is much smaller than the SLM. Further, the method isbased on the principle that the reconstruction of a single object pointonly requires a sub-hologram as a subset of the SLM. The informationabout each scene point is thus not distributed across the entirehologram, but is only contained in certain limited regions, theso-called sub-holograms. Following this concept, an individual objectpoint of the scene is only reconstructed by a limited pixel region onthe SLM, the so-called sub-hologram. The disclosure of WO 2008/025839 isbased on the idea that for each object point the contributions of thesub-holograms to the entire reconstruction of the scene can be retrievedfrom look-up tables, and that these sub-holograms are accumulated so asto form a total hologram for the reconstruction of the entire scene.

According to a particularly preferred example of the method disclosed inWO 2008/025839, a view of the scene is defined by the position of eachobserver and their viewing direction. Each observer is assigned with atleast one virtual observer window which lies near the observer eyes inan observer plane. In a preparatory process step the scene isdiscretised three-dimensionally into visible object points. These datamay already be taken from an interface. The steps of the processdisclosed in WO 2008/025839 are:

Step 1:

Finding the position of the sub-hologram for each object point: theposition and extent of the corresponding sub-hologram are derived fromthe position of an object point, i.e. its lateral x, y coordinates andits depth distance.

Step 2:

Retrieval of the contributions of the corresponding sub-hologram fromlook-up tables.

Step 3:

Repetition of these two steps for all object points, where thesub-holograms are accumulated so as to form a total hologram for thereconstruction of the entire scene.

According to a simple example disclosed in WO 2008/025839, the size of asub-hologram which is assigned to an object point is found based on thetheorem of intersecting lines. The observer window or a part thereofwhich covers the pupils is projected through the object point into thehologram plane, i.e. on to the SLM. The indices of the pixels of thesub-hologram which are required to reconstruct this scene point are thusdetermined.

According to a further aspect of the disclosure of WO 2008/025839,additional corrective functions are applied to the sub-holograms or thetotal hologram, e.g. in order to compensate SLM tolerances which arecaused by its position or shape, or to improve the reconstructionquality. The corrective values are for example added to the data valuesof the sub-holograms and/or of the total hologram. In addition, becauseevery sub-hologram is defined by the actual position of the observerwindow, special look-up tables can be generated for more unusualobserver windows, for example if the observer looks on the display at alarge angle from a side position.

The principle of using look-up tables can preferably be extended, asdescribed in WO 2008/025839. For example, parameter data for colour andbrightness information can be stored in separate look-up tables. Inaddition, data values of the sub-holograms and/or the total hologram canbe modulated with brightness and/or colour values from look-up tables. Acolour representation is therein based on the idea that the primarycolours can be retrieved from respective look-up tables.

The look-up tables on which the method disclosed in WO 2008/025839 isbased are preferably generated in accordance with WO 2006/066906 or WO2006/066919, which are filed by the applicant and are incorporated byreference. The look-up tables are then stored in suitable data carriersand storage media.

FIG. 26A illustrates the general idea of the disclosure of WO2008/025839 with the example of a single observer. A view of a scene (S)is defined by the position and viewing direction of an observer (O). Theobserver is assigned with at least one virtual observer window (VOW)which lies near the observer eyes in a reference plane. A modulated wavefield is generated from sufficiently coherent light by a spatial lightmodulator (SLM), which is controlled through hologram values. The methodand the display derived from that method are based on the idea not toreconstruct the object of the scene itself, but to reconstruct in one ormultiple virtual observer windows (VOW) the wave front which would beemitted by the object. In FIG. 26A, the object is represented by asingle object point (PP). The observer (O) can watch the scene (S)through the virtual observer windows (VOW). The virtual observer windows(VOW) cover the eye pupils of the observer (O) and can be tracked to theactual observer position with the help of known position detection andtracking systems. Controlling the spatial light modulator (SLM) with thehologram values of the video holograms thereby causes the wave field,which is modulated in pixels and emitted from the display screen, toreconstruct the three-dimensional scene as desired by generatinginterference in the reconstruction space. As can be seen from FIG. 26A,according to the general principle of this implementation, a singleobject point (PP) of the scene (S) is only reconstructed by a limitedpixel region on the spatial light modulator (SLM), the so-calledsub-hologram (SH). As can be seen in FIG. 26A, according to a mostsimple solution, the size of a sub-hologram (SH) are defined based onthe theorem of intersecting lines, whereby then the indices of thepixels required for the reconstruction of this object point (OP) arefound. The position and extent of the sub-hologram (SH) are derived fromthe position of an object point (PP), i.e. its lateral x, y coordinatesand its depth distance or z distance. Then, the hologram values requiredto reconstruct this point (PP) are now retrieved from the look-up tableLUT.

The sub-hologram (SH) is modulated with a brightness and/or colour valueand then accumulated into the hologram plane at the respective positionso as to form a so-called total hologram. The data contained in theabove-mentioned look-up tables are generated in advance. The data arepreferably generated using the method described in WO 2006/066906, ascited in the prior art section above, and stored in suitable datacarriers and storage media. With the help of the position and propertiesof the object points, the corresponding sub-holograms are computed inadvance and the look-up tables of the sub-holograms, colour andbrightness values and the corrective parameters are thus generated.

FIG. 26B illustrates this principle in more detail and shows thesub-holograms (SH1, SH2), which are assigned to the object points (P1,P2), respectively. It can be seen in FIG. 26B that these sub-hologramsare limited and form a small and contiguous subset of the totalhologram, i.e. the entire spatial light modulator (SLM). In addition tothe position and extent of the sub-holograms which are determined basedon the theorem of intersecting lines, as can be seen in FIG. 26, furtherfunctional relations are possible.

3. Discussion of Related Art

WO 2004/044659 (US2006/0055994) and U.S. Pat. No. 7,315,408B2, filed bythe applicant, and incorporated herein in their entirety by reference,describe a device for reconstructing three-dimensional scenes by way ofdiffraction of sufficiently coherent light; the device includes a pointlight source or line light source, a lens for focusing the light and aspatial light modulator. In contrast to conventional holographicdisplays, the SLM in transmission mode reconstructs a 3D-scene in atleast one ‘virtual observer window’ (see Appendix I and II for adiscussion of this term and the related technology). Each virtualobserver window is situated near the observer's eyes and is restrictedin size so that the virtual observer windows are situated in a singlediffraction order, so that each eye sees the complete reconstruction ofthe three-dimensional scene in a frustum-shaped reconstruction space,which stretches between the SLM surface and the virtual observer window.To allow a holographic reconstruction free of disturbance, the virtualobserver window size must not exceed the periodicity interval of onediffraction order of the reconstruction. However, it must be at leastlarge enough to enable a viewer to see the entire reconstruction of the3D-scene through the window(s). The other eye can see through the samevirtual observer window, or is assigned a second virtual observerwindow, which is accordingly created by a second light source. Here, avisibility region, which would typically be rather large, is limited tothe locally positioned virtual observer windows. The known solutionreconstructs in a diminutive fashion the large area resulting from ahigh resolution of a conventional SLM surface, reducing it to the sizeof the virtual observer windows. This leads to the effect that thediffraction angles, which are small due to geometrical reasons, and theresolution of current generation SLMs are sufficient to achieve ahigh-quality real-time holographic reconstruction using reasonable,consumer level computing equipment.

A mobile phone which generates a three dimensional image is disclosed inUS2004/0223049, which is incorporated herein in its entirety byreference. However, the three dimensional image disclosed therein isgenerated using autostereoscopy. One problem with autostereoscopicallygenerated three dimensional images is that typically the viewerperceives the image to be inside the display, whereas the viewer's eyestend to focus on the surface of the display. This disparity betweenwhere the viewer's eyes focus and the perceived position of the threedimensional image leads to viewer discomfort after some time in manycases. This problem does not occur, or is significantly reduced, in thecase of three dimensional images generated by holography.

SUMMARY OF THE INVENTION

A holographic display is provided including a spatial light modulator(SLM), and including a position detection and tracking system, such thata viewer's eye positions are tracked, with variable beam deflection tothe viewer's eye positions being performed using a microprism arraywhich enables controllable deflection of optical beams.

The holographic display may be such that the position detection andtracking system tracks viewers' eye positions, with variable beamdeflection to the viewers' eye positions being performed using themicroprism array which enables controllable deflection of optical beams.

The holographic display may be such that the variable beam deflection iscontinuously variable.

The holographic display may be such that variable beam deflection isperformed using electrowetting technology.

The holographic display may be such that variable beam deflection isperformed using variable voltage differences applied to differentelectrodes located on different sides of each of an array ofelectrowetting cells.

The holographic display may be such that two dimensional deflection isobtained by using two microprism arrays in series.

The holographic display may be such that the prisms are Micro LiquidPrisms.

The holographic display may be such that virtual observer windows (VOW)are placed at the viewer's or viewers' eyes.

The holographic display may be such that a focussing means placed beforeor after the prism array assists to converge the light rays into theVOW.

The holographic display may be such that an optical effect of lensaberration can be reduced by correcting dynamically through encoding ofthe spatial light modulator.

The holographic display may be such that the prisms do not all have thesame deflection angle.

The holographic display may be such that the prisms do not all have thesame deflection angle such that light rays exiting the prism arrayconverge somewhat at the VOW.

The holographic display may be such that a prism angle calculation isperformed in computational circuitry on a substrate of the SLM.

The holographic display may be such that a prism angle calculation isperformed in computational circuitry situated on a substrate of theprism array.

The holographic display may be such that the SLM's substrate is alsoused as the prism array's substrate.

The holographic display may be such that a phase correction is appliedto compensate for phase discontinuities introduced by the prism array.

The holographic display may be such that the phase correction isperformed by operation of the SLM.

The holographic display may be such that a holographic image isgenerated in a projection-type apparatus, where the projection involvesimaging the SLM onto the prism array while a reconstruction of a desired3D scene occurs in front of the VOW.

The holographic display may be such that phase compensation for theprism array is provided when imaging the SLM onto the prism array.

The holographic display may be such that phase compensation for theprism array is provided by an additional SLM placed near to the prismarray.

The holographic display may be such that the SLM is transmissive withthe prism array reflective.

The holographic display may be such that the SLM is reflective with theprism array transmissive.

The holographic display may be such that the SLM is transmissive withthe prism array transmissive.

A method is provided of generating a holographic reconstruction of athree dimensional scene, made up of multiple discrete points, using aholographic display according to the invention, the display including alight source and an optical system to illuminate the spatial lightmodulator; comprising the step of:

encoding a hologram on the spatial light modulator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram which shows that the data rate of the hologram ismuch higher than the data rate of the original real space data.

FIG. 2 is a diagram which compares the structure and performancecharacteristics of a portion of a prior art SLM with a portion of a SLMin which holographic calculation may be performed in the space of thepixel matrix.

FIG. 3 is a diagram of the structure of a portion of a SLM in whichholographic calculation may be performed in the space of the pixelmatrix.

FIG. 4 is a diagram of a portion of a SLM in which a decompressioncalculation may be performed in the space of the pixel matrix for thedisplay of holographic data.

FIG. 5 is a diagram of a portion of a SLM in which a decompressioncalculation may be performed in the space of the pixel matrix for thedisplay of conventional 2D display data.

FIG. 6 is a diagram showing views of a manufacturing process for TFTs.

FIG. 7 is a diagram showing views of a manufacturing process for TFTs.

FIG. 8 is a diagram of a method of reconstructing holograms according toan implementation.

FIG. 9 is a diagram of a method of reconstructing holograms according toan implementation.

FIG. 10 is a perspective view of a general structure of a conventionalactive matrix liquid crystal display device according to the prior art.

FIG. 11 contains views showing the fabrication steps of an active matrixsubstrate of a holographic display of an implementation.

FIG. 12 contains views showing the further fabrication steps of theactive matrix substrate of FIG. 11.

FIG. 13 contains views showing the further fabrication steps of theactive matrix substrate of FIG. 12.

FIG. 14 is a diagram of a holographic display with representation ofobject points at discrete and at arbitrary positions.

FIG. 15 is a diagram of functional units which may be implemented in thegraphics calculations in a holographic display of an implementation.

FIG. 16 is a diagram of a look-up table for sub-holograms SH used in aholographic display of an implementation.

FIG. 17 is a diagram of additional processing units for holographictransformation and encoding for a holographic display of animplementation.

FIG. 18 is a diagram showing that the computational load is much smallerif using sub-holograms, because of the smaller number of cells, for aholographic display of an implementation.

FIG. 19 is a diagram showing a scene at time t, a further scene at timet+1, and the difference scene.

FIG. 20 is a diagram showing a holographic display device of animplementation, with addressable data transfer.

FIG. 21 is a part of a spreadsheet in which is calculated the number oftransistors in a holographic display of an implementation.

FIG. 22 is the remainder of the part of the spreadsheet in FIG. 21.

FIG. 23 is a simplified diagram of a cluster design according to aholographic display device of an implementation.

FIG. 24 is a diagram of the paths taken by display data according to aholographic display device of an implementation.

FIG. 25 is a diagram of a portion of a SLM in which computationalcalculations may be performed in the space of the pixel matrix for adisplay which displays conventional 2D display data, or holographicdisplay data.

FIG. 26 is a diagram of a method of generating sub-holograms, accordingto the prior art.

FIG. 27 is a diagram of a method of reconstructing holograms accordingto an implementation.

FIG. 28 is a diagram of panel tiling according to an implementation.

FIG. 29 is a diagram of geometrical considerations relevant toocclusion.

FIG. 30 is a diagram of geometrical considerations relevant toocclusion.

FIG. 31 is a diagram of a method of dealing with occlusion phenomena,according to an implementation.

FIG. 32 is a diagram of a method of dealing with occlusion phenomena,according to an implementation.

FIG. 33 is a diagram of the paths taken by display data according to aholographic display device of an implementation.

FIG. 34 is a diagram of a method of tracking one or more users by movingthe virtual observer window using controllable prisms, according to animplementation.

DETAILED DESCRIPTION A. Hologram Display with Calculation on the SameSubstrate as the Pixels

An implementation includes a display which receives real space imagedata, such as an intensity map and a depth map corresponding to a threedimensional image. The holographic encoding of the spatial lightmodulator is then calculated in real time or in quasi real time based onthe three dimensional image data. At least some of the hologramcalculations may be performed in the physical space in which the pixelmatrix exists, by combining two functional units, namely the hologramcalculation unit and the hologram display unit, which are separatefunctionally and spatially in prior art devices, so as to form a commonunit which is implemented on one substrate. This means that transistorsfor at least some of the hologram calculation may be integrated between,or next to, the transistors used for pixel control. Alternatively, allthe hologram calculations may be performed in the physical space inwhich the pixel matrix exists, by combining two functional units, namelythe hologram calculation unit and the hologram display unit, which areseparate functionally and spatially in prior art devices, so as to forma common unit which is implemented on one substrate. Alternatively, someor all of the transistors for the hologram calculation may be outsidethe pixel matrix, but on the same substrate as the transistors used forpixel control. It should be clear to those skilled in the art that bythe term “on the same substrate” it is not meant that the transistorscan only be in atomic level contact with the substrate, but rather thatthe substrate generally provides the physically supporting medium onwhich the circuitry is disposed. Further information on the meaning of“substrate” is given in the section entitled “SUBSTRATE”.

The calculation of holograms in the pixel matrix, or elsewhere on thesame substrate, is not limited to the analytical hologram calculationmethods described in the prior art. Other types of calculation methodsuch as look-up table (LUT) approaches are also possible. An analyticalcalculation method may be used as an example to demonstrate thecalculation method. For the calculation of holograms in the pixelmatrix, the holographic computation method may be identical over thewhole display and it is preferred to exchange data for adding the subholograms over the distance of about a sub-hologram dimension.Sub-holograms are used for computation. It is possible to spread thecomputation homogeneously over the whole display surface. But to easehardware design, simulation and verification it is possible to dividethe computation into small identical parts called clusters tiled overthe display surface. The tiles need not be rectangular and otherstructures like tiled hexagons (“honeycomb”) are also possible. The name“cluster” is used for a computation unit which covers part of or thewhole of the hologram computation data path. So a cluster can be thesmallest unit able to compute the hologram data for a tile of thedisplay from a section of original real space data. These clusterspreferably exchange data between neighbouring units, so that wheresub-holograms from neighbouring units overlap, the SLM can be correctlyencoded. This is shown schematically in FIG. 24. One advantage of thecluster approach is after the cluster is designed, the holographicdisplay can be built up easily through tiling identical clusterstogether.

Ideally, very high resolutions, e.g. 16,000×12,000 pixels, are requiredto display holograms with very high image quality, or with a virtualobserver window which is the order of one or more cm across rather thana few mm across, or both. The image content to be displayed, comprisingan intensity image and three-dimensional depth information (which can bereferred to as a “Z buffer”), typically have a resolution of up to2,000×1,500 pixels only. As shown in FIG. 1, the data rate required todisplay the hologram is much higher than the data rate required todisplay the original data, e.g. by a factor of 48 with the examplevalues given. In FIG. 1, three dimensional image data is supplied in theform of an intensity map and a three dimensional depth map. Preferablyone depth map and intensity map pair should be constructed for each eyei.e. for each virtual observer window. Each of these maps consists of adata array of 2,000×1,500 pixels. The data for each pixel in each map isrepresented by three colours and one z-value, i.e. four values, of eightbits each. A bit is a binary digit. So 32 bits per pixel are needed.Video data is provided at 25 Hz, or 25 frames per second (fps). Usingtwo views (right eye and left eye) the data rate is 4.8 Gbits persecond, as shown. This data is used to calculate the hologram, on aframe-by-frame basis in a simple case, although some data processinginvolving successive frames may be performed in more sophisticatedexamples, for example, such as to smooth noise or to reduce artefacts,or to reduce the required data transmission rate, for example. Thehologram computation produces data output corresponding to a data arrayof 16,000×12,000 pixels, where each pixel is represented by eight bits,and the frame rate is 150 fps, using a 25 Hz video rate and two viewsand three colours. Hence the data rate for the hologram is 230 Gbits persecond, as shown. The contents of FIG. 1 represent the process in whichthe three primary colours red, green and blue are displayed. Thisexample relates to a single user configuration, but multi userconfigurations, with correspondingly higher display frame rates, arealso possible. Many other examples of data rates in holographic displayswill be obvious to those skilled in the art.

It should be emphasized that a frame rate of about 25 Hz is the minimumacceptable rate for moving images. A frame rate higher than 25 Hz shouldbe used for a smoother playback. The higher the frame rate, the smootherthe playback will appear to the viewer.

A hologram can only be calculated for a given display opticalwavelength. This is why the calculation is performed three times foreach object point, i.e. once for each component colour, e.g. red, greenand blue. Other colours can be created by utilizing the three colourcomponents, and this colour mixing can be realised either sequentiallyor simultaneously.

If the hologram is generated in circuitry on the same substrate, e.g. inthe pixel matrix, only the original image data need be transmitted tothe display substrate. Where the hologram is generated using circuitryin the pixel matrix, the intensity and depth information are transportedto those positions in the panel where they will be needed later forhologram calculation. In the preferred display of an implementation, inorder to calculate the value of a pixel of the hologram, only values ofa sub-section of the original image will be considered. One reason forthis is that in the preferred display of an implementation, the lightused for the reconstruction is not fully coherent across the entiredisplay, but rather coherence exists within sub-sections of the display,which may be small sub-sections of the display. Coherence does notexist, or exists only to a limited extent, from one sub-section of thedisplay with respect to a different sub-section of the display. Eachsub-section of the preferred display may be used to generate acorresponding sub-hologram of the whole hologram. The dimensions of asub-hologram thus define the maximum extension of the region around apixel from which intensity and depth values of the original image arerequired for calculation of the sub-hologram. This in turn defines thelengths of the necessary internal wires, the so-called “localinterconnections”: see FIG. 3. Because, according to this solution, allor at least some of the large amount of pixel data required to generatethe hologram is calculated directly at those areas on the display panelwhere they will be displayed, there is no need, or the need is reduced,for transfer of holographic display data through long wires or forintermediate storage of data. This will reduce the resolution of thedata to be sent to the display panel and thus it will reduce the datarate to be sent to the display panel. If the example is applied to thesituation shown in FIG. 1, a reduction by a factor of about 50 in thedata transmission rate is achieved. Consequently, the number of row andcolumn wires which run across the entire panel, the so-called “globalinterconnections”, cf. FIG. 3, will be reduced correspondingly. Fewerwires will be sufficient for the transfer of original image data thanfor the transmission of hologram data, and the transmission frequencycan be reduced correspondingly, which has the additional benefit ofcutting the electrical power dissipation in the row and column drivers.

Reducing the data transmission frequency has the benefit of reducing thepower dissipation in the row and column drivers. This is becauseswitching a binary digit from zero to one, or vice versa, requireselectrical power. As the switching rate rises, the electrical powerrequirement rises. The power is eventually dissipated as heat, which maylead to thermal problems in high data transmission frequency displays.Thermal problems may include components becoming dangerously hot to thetouch, cracking and failure in electronic components as a result ofthermally induced stress, unwanted chemical reactions such as oxidationof electronic components, degradation of the quality of liquid crystalmaterial as a result of exposure to extreme temperatures, and changes tothe behaviour of semiconductor materials, such as thermal carriergeneration, as the result of elevated temperatures. If the device runson batteries, these will discharge more quickly if more power is drawnfrom them, which will reduce the time the device can be used betweenbattery charging.

The large proportion of the area per pixel which was required in priorart solutions for column and row wires can now be used for otherpurposes. FIG. 2 compares the working principles of the two solutions.In the solution based on the prior art, a high resolution holographicdisplay with 16,000×12,000 pixels is considered. To shorten the row andcolumn lines the display is tiled into 4 quadrants, as shown for examplein FIG. 28. Each quadrant has 8,000 column wires and 6,000 row wires. Intotal, 32,000 column wires and 24,000 row wires are needed. For one userthe two views (right and left) with three component colours (e.g. R, G,B) each at 25 fps video rate (the frame rate of the input data—intensityand z-buffer) result in a display frame rate of 150 images per second.Multiplying by the row numbers and adding 10% for blank transmissiontime between frames, a 1 MHz column driving frequency is required. In anexample of a solution according to an implementation, image data issupplied according to a real image pixel array of 2,000×1,500 pixels. Ifthe display is also tiled into 4 quadrants, each quadrant has 750 rowwires. Multiplying this by 150 images per second and adding 20% forblank transmission time between frames, only a 135 kHz column drivingfrequency is needed, as indicated. This example relates to a single userconfiguration, but multi user configurations, with correspondinglyhigher display frame rates, are also possible.

Depending on the panel and calculation parameters, the space saving inrow and column wires which may be omitted in the solution according tothe implementation of FIG. 2, when compared to the solution according tothe prior art of FIG. 2, may be greater than the space needed forcircuitry for hologram calculation, so that only a part of the savedspace will be needed for the transistors used for hologram calculation.In this case, the area of the transparent electrode can be increased andthus the transmittance of the LCD can be improved. Because thecalculation is carried out in the saved pixel area, an additionalcalculation unit which is not on the same substrate as the display, andwhich would cause considerable difficulties and costs in any knownconventional device, becomes redundant. Another advantage is the factthat complexity of the panel control is reduced greatly, because thedata rate for panel control is about the same as with conventional LCDs.The data rate of 4.8 Gbit/s for an exemplary resolution of 2,000×1,500pixels at 25 fps and two views with 32 bits per pixel is about the sameas that for a TFT panel with 1,920×1,600 pixels with a 60 Hz frame rateand with three 8 bit colours. This example relates to a single userconfiguration, but multi user configurations, with correspondinglyhigher display frame rates, are also possible. This means that such apanel can be controlled easily with conventional display technologies,whereas the transmission of the entire hologram with the exemplary datatransfer rate of 230 Gbits/s of FIG. 1, both between the calculationunit and display electronics, and between display electronics and thedisplay panel would only be feasible using special solutions which wouldbe difficult to implement and would also be very expensive, as would beappreciated by one skilled in the art.

If we consider the two-dimensional encoding of a hologram on a spatiallight modulator, where the original real space image has 2,000×1,500pixels and is supplied at a video frame rate of 25 fps, about 100million transistors would be needed roughly for the holographiccalculation i.e. about 34 transistors per real space pixel. This is formonocrystalline Si circuitry, with a switching frequency of 200 MHz.Because a TFT made of polycrystalline Si may have a switching frequencyof only about 25 MHz, about 690 million transistors, instead of 100million transistors, would be necessary to compensate for the lowerswitching speed. Given a hologram resolution of 16,000×12,000 pixels,this would mean about 4 transistors per hologram pixel. Because thecalculated values can only be written to the pixel cell when a new imageis to be displayed, an additional 1 or 2 transistors would be requiredper pixel. The larger the dimensions of a display while keeping the sameresolution, the larger will be the pixel pitch and thus the larger willbe the number of transistors which can be additionally arranged around apixel. A more detailed estimation of transistor count is given in theESTIMATION OF TRANSISTOR COUNT section.

If the panel is controlled via row and column wires, these wires shouldbe wider the larger the display. This is because for fixed wire materialelectrical resistivity, and for fixed wire cross sectional area, thewire's electrical resistance is proportional to its length; for fixedwire material electrical resistivity, and for fixed wire length andthickness, the wire's electrical resistance is inversely proportional toits width. This means that the method of calculating the hologram in thepixel matrix is advantageous with respect to classic controltechnologies in particular with large and high-resolution holographicdisplays.

An integration as TFT transistors has the great advantage that thetransistors for calculation are applied on to the substrate togetherwith the pixel transistors.

Additional costs would only be incurred insofar as the increased numberof transistors may result in a greater failure probability. This couldbe compensated by using a fault-tolerant calculation method, wherefaults in individual elements would only cause small deviations from thecalculation result that would be obtained if no components weredefective.

The calculation would be conducted in many neighboring computing unitscalled clusters in FIGS. 2 and 3. Generally, the size of the computingunits (clusters) is to be optimised, because the greater their size thesmaller the saving in the data transfer rate on the one hand, but theeasier the realisation of the calculations on the other.

In a further example of an implementation, a display is used to displayholographic image data which has been computed based on real space datasuch as intensity map and depth map data. An inherent problem withdisplays of the prior art is that they require circuitry which is notimplemented on the same substrate as the display circuitry. Thisadditional circuitry must be implemented on a separate substrate to thedisplay substrate. This leads to undesirable properties such as greaterdevice volume and weight. Consumers are constantly demanding displaydevices which are smaller, slimmer, or lighter. The holographic displayof an implementation has computational circuitry which is on the samesubstrate as the display circuitry. The computational circuitry may bebetween the pixels of the display, or it may be outside the pixel arrayof the display, but still on the same substrate.

Notes on the Integration in Liquid Crystal on Si (LCoS) Displays

Things are somewhat different with small LCoS displays, which areapplied to a mono-crystalline silicon wafer. Much higher frequencies arepossible with this display technology, so that may be even less than onetransistor per pixel will be sufficient for the holographic calculation.Generally, the calculation could largely be the same as the discretecalculation, the computing units would only be interrupted by the pixelcells. Because the Si area needed for calculation remains the same,savings may be achieved here by the fact that smaller amounts of datawill be transferred or stored only. This reduces the area required forrow and column wires and facilitates the transfer of data to the LCoS.However, the computational circuitry could be on the same substrate asthe display circuitry, with the computational circuitry not beinglocated within the display circuitry, as the solution would be morecompact and cheaper than if the computational circuitry were on adifferent substrate to the display circuitry.

Local Forwarding

Because an additional logic for local forwarding of calculated dataalready exists, it can also be co-used for forwarding the original imageto the respective regions, so that global row and column wires becomesuperfluous entirely. The original data would for example be forwardedfrom cluster to cluster using a shift register. Because the row controlis carried out locally, the omission of row wires makes it possible alsofor the right and left hand side of the display to be used for writinginformation.

Fault-Tolerant Computing Units

Already with normal TFT displays which have a resolution of for example1,600×1,200 pixels, there can be manufacturing errors, which becomeapparent as pixel errors. High-resolution displays in holography have amuch higher number of pixels and thus a much higher number of TFTs,which increases the probability of pixel errors greatly. If additionalTFTs are integrated for calculation, the error rate will rise again.This makes it necessary to design the calculation process such thaterrors in single faulty TFTs do not propagate through the entiredisplay, but only cause small local deviations from ideal performance.

It may be possible that some manufacturing errors lead to consequencesthat are not visible to the viewer, or are only marginally perceivableby the human vision system. In this case one may tolerate such defects.But for example a completely damaged cluster is intolerable, since a lotof SLM cells are affected in such an instance.

Redundant circuitry, such as TFTs, may be manufactured in the space ofthe pixel matrix so that such circuitry can be used to replace some ofthe circuitry used at device start up, if some of the circuitry used atdevice start up is found to have failed. A device may self-test fromtime-to-time, such by testing if the switching characteristics of apiece of circuitry indicates circuitry malfunction or not.Malfunctioning circuitry may be recorded in memory, such as non-volatilememory, as being unusable, and other circuitry recorded as being used inits place. A similar approach has been reported for fault-tolerantconventional computer circuitry in “Physics and the InformationRevolution” J. Birnbaum and R. S. Williams, Physics Today, January 2000,pp. 38-42, which is incorporated herein by reference. Alternatively, thecircuitry may be designed such that the probability of failure resultingin a permanently dark pixel is greater than the probability of failureresulting in a permanently bright pixel, as the latter is moreirritating for the viewer.

For optimized error tolerance design, at the more important placeswithin the circuitry larger component-size transistors, especially withlarger lateral sizes, may be implemented to reduce the probability offailure of the more important parts of the circuitry. A further approachis to mix the calculation pipelines so that results of a defective unitare distributed over a larger surface area. This may be understood ifone appreciates that to calculate the value of a hologram pixel about1000 or more values may be added. If these values all came from the samepipeline, the hologram pixel value will be a completely wrong value ifthis pipeline fails. If a cluster consists of parallel pipelines, theinternal cluster structure can be arranged in a way that the values foradding come from all the parallel pipelines. If the values come from forinstance 4 pipelines, then if one pipeline fails only 25% of the inputvalues will be incorrect. In this instance, the calculated hologrampixel value will be more accurate than if 100% of the input values wereincorrect.

A “subsequent repair” strategy may be used in some cases. In such cases,one identifies the failed units during the test phase of the display andone then modifies the circuitry by physically cutting the relevantconducting lines. Such an approach may resolve short circuits. The cutconnections may ensure that the most undesirable pixel failures (e.g.pixels shining constantly with high intensity) can be improved by simplyswitching them off, leaving them dark.

For devices according to implementations, the devices may bemanufactured according to the OUTLINE MANUFACTURING PROCESSES givenbelow, or some combination thereof, or according to other manufacturingprocesses that are obvious to those skilled in the art. Organicsemiconductors may also be used to manufacture the circuitry withindevices of implementations.

B. Hologram Display with Calculation on the Same Substrate, withEfficient Calculation of the Encoding for the Spatial Light Modulator

Known methods for the transformation of three-dimensional content forthe representation of large computer-generated holograms (CGH) forreconstructions which vary in real-time or in quasi real-time could onlybe realised with great efforts as regards computational resources. In animprovement described in the prior art patent application “Method forgenerating computer-generated video holograms in real time with the helpof LUTs”, publication no. WO 2008/025839, interactive real-timeholograms with 1920×1080 reconstructed object points can be displayedinteractively in real-time with commercially available personal computer(PC) systems using pre-calculated sub-holograms and with the help oflook-up tables (LUTs). The prior art method is characterised in that theobject points can only be reconstructed at certain discrete positions,as shown in FIG. 14 by the open circles. The method of an implementationdescribed here circumvents this restriction in that the object pointscan be generated at any position within the reconstruction frustum, asshown in FIG. 14 by the closed circles. FIG. 14 shows how object points(open circles), which are generated using the prior art LUT method, arefixedly assigned to certain object planes. The object planes, in turn,are positioned at fixed distances to the hologram plane. In contrast,according to the analytic method of an implementation, the object points(filled circles) can be at any position.

The implementation of part A may be implemented using prior art methodsfor calculating the encoding of the spatial light modulator.Alternatively, the implementation of part A may be implemented using amethod which provides a more efficient calculation of the encoding forthe spatial light modulator. One more efficient calculation method isthat described in publication no. WO 2008/025839. The following moreefficient method, which does not require the calculation of Fouriertransforms or Fresnel transforms per se and therefore can be implementedefficiently, is an implementation of the applicant. It may also be saidthat the following more efficient method does not require thecalculation of Fourier transforms or Fresnel transforms.

An example of the method, which provides a more efficient calculation ofthe encoding for the spatial light modulator, is as follows. It is ananalytic method, described with reference to FIGS. 8 and 9, for thegeneration of computer-generated video-holograms for a holographicdisplay device (HAE), comprising an SLM light-modulating-means (SLM1)and where the wavefront which would be emitted by the object isreconstructed in one or multiple virtual observer windows (VOW) andwhere the reconstruction of each single object point (OP) of athree-dimensional scene (3D-S) only requires a sub-hologram (SH) as asubset of the entire hologram (HΣ_(SLM)) to be encoded on the SLM,characterised in that after a discretization of the 3D-scene (3D-S) tomultiple object-points the method comprises the following steps:

for each visible object-point (OP) of the 3D-scene

Step A: Determination of the Position of the Sub-Hologram (SH) for EachObject Point (OP).

-   -   For example, using the theorem of intersections, where a virtual        visibility-region is projected through the object-point from the        hologram-plane, to the SLM itself. With sufficient accuracy the        sub-hologram can be approximated/modelled as a rectangle. A        local coordinate-system is assigned to the sub-hologram, with an        origin at its centre; the x-coordinate is the abscissa and the        y-coordinate is the ordinate. The sub-hologram has dimensions as        the half width and “b” as the half height.

Step B: Determination of the Sub-Hologram of the Virtual Lens (L) forEach Sub-Hologram (SH) Within the Hologram-Plane (HE):

-   -   B1: Determination of the focal length (f) of the virtual lens        The focus length (f) of the lens is the orthogonal distance from        the SLM of the object-point (OP) to be reconstructed in the        hologram-plane (HE).    -   B2: Complex values of the sub-hologram (SH_(L)) of the lens: The        complex values of the sub-hologram are determined using the        formula        z _(L)=exp{−i*[(π/λf)*(x ² +y ²)]}    -   with λ as the optical reference-wave-length, and f as the focal        length. A positive sign for f in the equation corresponds to a        convex lens, as shown in FIG. 9A. A negative value of f is        required if a virtual diverging lens were used to reconstruct an        object-point (OP) on the opposite side of the SLM to the viewer,        as shown in FIG. 27.    -   B3: Due to the symmetry of z_(L) with respect to positive and        negative values of x and y, it will be sufficient to determine        the values of z_(L) in one quadrant and to transfer the results        to the other three quadrants, using the appropriate sign.

Step C. Determination of the Sub-Hologram (SH_(P)) of the Prism withinthe Hologram-Plane (HE):

-   -   Due to the chosen local coordinate-system, a prism will result        in a phase-shift, whereby the phase-shift is a linear function        of the x and y coordinates.    -   C1: Determination of the linear factor C_(x) of the prism (P)        with horizontal effect, described within the interval x∈[0, a]        as    -   C_(x)=M*(2π/λ); with M as the absolute prism slope (FIG. 9B)    -   C2: Determination of the linear factor C_(y) of the prism (P)        with vertical effect, described within the interval y∈[0, b] as    -   C_(y)=N*(2π/λ); with N as the absolute prism slope (FIG. 9C)    -   C3: Complex Values of the sub-hologram (SH_(P)) of the prism:        The complex values of this sub-hologram (SH_(P)) are determined        by the superposition of the prisms, with        z _(P)=exp{i*[C _(x)*(x−a)+C _(y)*(y−b)]}    -   C4: The prism correction may be neglected if the light source is        imaged to the VOW by the holographic display device.

Step D: Modulation of the Sub-Holograms of the Lens and of the Prisms:

The complex values of the combined sub-hologram are given by a complexmultiplication of the effects of the virtual lens (L) and the virtualprism (P), shown in FIG. 9A, as z_(SH)=z_(L)*z_(P), which can berepresented symbolically as SH=SH_(L)*SH_(P)

Step E: Phase Shift

Each sub-hologram (SH) is modulated with a (uniformly distributed) phaseshift, where the phase shift is different from sub-hologram tosub-hologram, in order to achieve homogenous illumination within thevisibility-region. This can reduce speckle patterns from light sourceswith optical coherence. The magnitude of the phase shift is sufficientto reduce the speckle pattern, and may be less than π radians (i.e. notnecessarily −π<Φ₀<π, but e.g. −π/4<Φ₀<π/4). This process may berepresented by:z_(SH):=z_(SH)exp(iΦ₀), which can be represented symbolically as SH:=SHexp(iΦ₀)

Step F: Intensity Modulation

The complex values, respectively the sub-holograms, are modulated withan intensity-factor obtained from the frame buffer content (monochromeor colour e.g. R, G, B) so that object points represent their ownbrightness, and colour if appropriate

z_(SH)=C*z_(SH), which can be represented symbolically as SH:=C*SH;

Step G: Adding the Sub-Holograms to Form an Entire Hologram HΣ_(SLM).

-   -   The sub-holograms can be superposed using complex addition. The        entire hologram is the complex sum of the sub-holograms given by    -   HΣ_(SLM)=ΣSH_(i), which can be represented symbolically as        Z_(SLM)=Σz_(SH), according to a coordinate-system for the whole        hologram.

Steps C, D, and E in the above may be omitted individually or incombination in some examples of implementations, where computationalpower or the quality of the hologram may be reduced in return for somebenefit such as reduced manufacturing cost of the hardware required toimplement the above calculation method.

Further remarks are that if the reconstructed object point is consideredto be the focal point of an optical system, this means that there is alens in the hologram plane, said lens being inclined and having thefocal length f. An inclined lens is composed of a non-inclined lens anda prism. According to the method presented here, an object point isreconstructed such that a lens function and, if necessary, a prismfunction are encoded in a sub-hologram (see FIG. 9A). A scene, which iscomposed of a multitude of points, can be generated by superimpositionof sub-holograms. Through the use of this method, object points for aninteractive real-time holographic reconstruction can be generated at anyposition in the reconstruction frustum using standard hardwarecomponents which are commercially available. This solution is alsoreadily resizable as regards the number of object points. The number ofobject points can be increased as the performance of the processing unitrises.

The Calculation Process May be Summarized as:

1. Calculation of the lens

-   -   a. Finding the focal length f    -   b. Use of lens equation: e^{−i*[(π/λf)*(x²+y²)]}        2. Calculation of the prism term (optional, depending on the        process)    -   a. Determining Cx, Cy, a and b    -   b. Equation: e^{i*[Cx*(x−a)+Cy*(y−b)]}        Cx=(2π/λ)*m        Cy=(2π/λ)*n        3. Modulation of the prism and lens terms (optional, depending        on the process)        4. Application of the random phase (optional, depending on the        process)        5. Intensity modulation        6. SLM-specific encoding of the hologram

C. Hologram Display with Decompression Calculation on the Same Substrate

An implementation includes a display which receives real space imagedata, such as an intensity map and a depth map corresponding to a threedimensional image. The holographic encoding of the spatial lightmodulator is then calculated in real time or in quasi real time based onthe three dimensional image data. All or at least some of the hologramdisplay calculations may be performed in the physical space in which thepixel matrix exists, by combining two functional units, namely thehologram display calculation unit and the hologram display unit, whichare separate functionally and spatially in prior art devices, so as toform a common unit which is implemented on one substrate. This meansthat transistors for all or at least some of the hologram displaycalculation are integrated between or next to the transistors used forpixel control. Alternatively, the hologram display calculation may beimplemented using circuitry which is on the same substrate as the pixelcircuitry, but where the hologram display calculation circuitry isoutside the pixel circuitry.

In this further example of an implementation, the hologram calculationis performed at a location which is not within the space occupied by thepixel matrix. Such a calculation may take advantage oflocally-accessible look up tables (LUTs), as described in publicationno. WO 2008/025839, which increases the computational efficiency of thecalculations. As FIG. 1 makes clear, a problem with an approach wherehologram calculation is performed outside the space of the displaypixels is that very high total data transmission rates to the pixels ofthe display are required. This may be avoided if an approach such as theapproach of FIG. 4 is adopted.

In the display, the hologram encoding data is calculated outside thespace occupied by the pixel matrix. The space in which thesecalculations are performed may or may not be on the same substrate asthe display's substrate. The hologram encoding data is compressed usingknown data compression techniques, and is then transmitted to thedisplay clusters which are part of the whole display. In FIG. 4, theTFTs for hologram calculation perform the function of decompressing thedata which has been received via the row and column wires. However, thedata could also be received via other means, such as via a parallel databus, or a serial data connection. Hologram display on acluster-by-cluster basis with reduced requirements for interconnectionbetween the hologram display pixels and the source of the imageintensity maps and image depth maps is thereby permitted. It is alsopossible that the hologram calculation and data compression could beperformed outside the display substrate, with data decompressionperformed using circuitry on the same substrate as the pixels of thedisplay, but where decompression is performed outside the space of thepixel matrix. Other examples will be obvious to those skilled in theart.

D. High Resolution Display with Decompression Calculation on the SameSubstrate

In a further example of an implementation, a high resolution display isused to display high resolution image data, which may be normal displaydata or may be hologram display data which has been computed based onintensity map and depth map data. Inherent problems with high resolutiondisplays of the prior art is that they require high density circuitrywhich is prone to fabrication errors, and they require high switchingfrequencies which can lead to problems with excessive heat generation.These problems may be reduced or avoided if an approach such as theapproach of FIG. 5 is adopted.

In the high resolution display, image data is compressed inside oroutside the display using known data compression techniques, and is thentransmitted to the display clusters which are part of the whole display.The space in which the compression calculations are performed may or maynot be on the same substrate as the display's substrate. In FIG. 5, theTFTs for the decompression calculation perform the function ofdecompressing the data which has been received via the row and columnwires. However, the data could also be received via other means, such asvia a parallel data bus, or a serial data connection. For minimum memoryrequirements, at a 25 Hz frame rate the TFTs for decompressioncalculation would be required to decompress this data for display by thepixels of the cluster in about 40 ms or less. Image display on acluster-by-cluster basis with reduced requirements for interconnectionbetween the image display pixels and the source of the image intensitymaps is thereby permitted. Other examples will be obvious to thoseskilled in the art.

In a preferred example, compressed real space image data is sent to theclusters of the display. In a first step, the clusters perform adecompression of the compressed real space image data. In a second step,holographic display data is computed by the clusters of the displayusing the data produced by the first step. Other examples will beobvious to those skilled in the art.

E. Hologram Display with Calculation on the Same Substrate, with anExtended 3D Rendering Pipeline for the Graphics Sub-Systems byIncorporating Additional Processing Units for Holographic Transformationand Encoding

The implementation of part A may be implemented using prior art methodsfor encoding the spatial light modulator. Alternatively, theimplementation of part A may be implemented using a method whichprovides a more efficient encoding of the spatial light modulator. Anexample of the method, which provides a more efficient encoding of thespatial light modulator, is as follows, but many other examples will beobvious to those skilled in the art.

The method, an example of which is shown in FIG. 15, extends the 3Drendering pipeline of graphics sub-systems by incorporating additionalprocessing units for holographic transformation and encoding. The methodis an implementation of the applicant. The expression “additionalprocessing units for holographic transformation and encoding” will bereplaced by the term “holo-pipeline” in what follows. The holo-pipelineis arranged directly downstream the 3D graphics pipeline. The 3Dpipeline data for each cluster is sent to the corresponding cluster inthe display; the description from here focuses on the implementation atthe level of a single cluster. A Z map buffer and a colour map buffer(colour map R, colour map G, colour map B) form the interface betweenthe two pipelines. This is shown schematically in FIG. 15. For eachindividual point in pixel coordinates the Z map contains a z value,which is scaled and which can be represented at various definitionlevels. Z values are typically scaled in a range of between 0.0 and 1.0,but other ranges are possible. The definition level is determined by thenumber of bits, i.e. usually 8, 16 or 24 bits.

In modern graphics sub-systems, the colour map has a definition of 24bits, i.e. 8 bits per colour component, R, G, B (red, green, blue). Thecolour map forms a part of the frame buffer, whose content is normallydisplayed on the screen. The two buffers, which contain the Z map andthe colour map, are defined to form the interface between the 3Drendering pipeline and the holo-pipeline. The Z map is provided for onedisplay wavelength, but this is no particular wavelength of R, G, B.Copies of the Z map 1501 and 1502 are provided for the other two displaywavelengths.

A hologram can only be calculated for a given display opticalwavelength. This is why the calculation is performed three times foreach object point, i.e. once for each primary colour, red (λR), green(λG) and blue (λB). Other colours can be created by utilizing thesethree colour components, and this colour mixing can be realised eithersequentially or simultaneously. In order to increase the processingspeed, at least two additional holo-pipelines are used, so that hologramcalculations are performed in parallel. The results for all three colourcomponents will then be available at the same time. For this, it isnecessary that the z map data are copied to additional memory sections1501 and 1502 (see FIG. 15), which can be accessed independently of oneanother. It is thereby prevented that operations which involve memorysections such as z map data can block each other. The memory sectionsshould therefore ideally be separated physically. The colour map RGBcontents for colours G and B are also copied to separate memory sectionscolour map G, and colour map B, respectively, so as to ensureindependent access to the three colour components (see FIG. 15). Again,the memory sections may be separated physically in order to preventcollisions during memory access and to reduce or eliminate difficultimplementations problems for access synchronisation with semaphores,mutual exclusion algorithms (or “mutexes”), etc., which would adverselyaffect system performance. Nevertheless, while the memory sections maybe separated physically from each other, they should still preferably belocated within the same cluster of the display. Note that a semaphore isa protected variable (or abstract data type) and constitutes the classicmethod for restricting access to shared resources (e.g. storage) in amultiprogramming environment; mutual exclusion algorithms are used inconcurrent programming to avoid the simultaneous use of a commonresource, such as a global variable, by pieces of computer code calledcritical sections.

It will be assumed below that a hologram is composed of a number ofsub-holograms. The m-th sub-hologram is therein represented by a lenswhich is described by a lens function: e^(−i C_(t)*(x_(m) ²+y_(m) ²)).The constant C_(t) includes the focal length f of the lens; the value off is calculated before the lens function is applied, so that the valueof f can then be used for all three pipelines. The value of f istherefore not colour-specific: because it is a virtual lens it need notexhibit chromatic aberration. It is possible to take advantage of thelens function relation, because a lens is symmetrical as regards its xand y axes. In order to describe a lens in full, the function need onlybe applied to one quadrant. The lens function values calculated in onequadrant can then be applied to the other three quadrants by using asymmetry rule of sign.

C_(t) also depends on the wavelength λ which naturally differs among thethree colours, R, G, B. The value of λ does not have to be calculated,because it is known due to the fact that a defined laser or light sourceis used for each wavelength; however, the value of λ should be madeavailable within the calculation in order to calculate C_(t) for eachprimary display colour (see FIG. 15).

Depending on the process used, it may become necessary that in additionto the lens function a prism function (see FIG. 15) should be applied inorder to modify the direction of light propagation. In the prismfunction, a constant also includes the wavelength λ. The value of thatconstant thus varies because the three primary colours have differentwavelengths, so that the value of that constant has a specific value foreach of the three holo-pipelines.

Both the lens function and the prism function now undergo a complexmultiplication at 1503, 1504 and 1505, shown in FIG. 15. Then, a randomphase is applied at 1506, 1507 and 1508, which is added to the result ofthe multiplication of lens and prism function. This method aims to avoidbrightness peaks, or “speckle,” in the observer plane. The intensity ofthe respective colour map is then used to modulate the respectivehologram at 1509, 1510, 1511.

In a next step, this sub-hologram undergoes a complex addition to formthe total hologram for the cluster (see FIG. 15). The results are nowavailable for subsequent processing, if applicable, using additionalalgorithms in the holographic display cluster, e.g. the application ofcorrection maps or greyscale images (gamma correction), which are onlydetermined by the system properties of the SLM, so that they arepreferably corrected at this stage. This is followed by the encodingprocess. The hologram may be reconstructed in colour. The encodingalgorithms (see FIG. 15) vary greatly depending on the SLM used, whichcan be phase-encoded, amplitude-encoded or encoded in another way.

The person skilled in the art will recognize that some aspects of theimplementation given in this section are disclosed in greater detailelsewhere within this application.

F. Hologram Display with Calculation on the Same Substrate, withSequential Holographic Transformation of Points in Three-DimensionalSpace by Way of Extending the 3D Pipeline of Graphics Cards with aHolographic Calculation Pipeline

The implementation of part A may be implemented using prior art methodsfor performing the holographic calculations. Alternatively, theimplementation of part A may be implemented using a method whichprovides a reduced time delay for performing the holographiccalculations. An example of the method, which provides a reduced timedelay for performing the holographic calculations, is as follows, butmany other examples will be obvious to those skilled in the art.

An object of the implementation is, for a hologram display withcalculation near the pixels, to reduce the time delay compared withother holographic calculations. This will result in an extension of thearchitecture of e.g. currently used graphics cards (3D pipeline) byadditional hardware modules for real-time holographic transformation andencoding.

In general, before a holographic transformation calculation isperformed, the entire three-dimensional scene is composed by realisingseveral 3D transformations and illumination calculations. The primitives(e.g. points, lines, triangles), which make up the objects of the scene,will be pixelated at the end of the 3D processing pipeline. The entireresult is then available in two memory sections. These are a framebuffer, which contains the colour values (colour map) of the sceneviewed by the observer, and a Z buffer, which contains the depth map ofthe scene in a scaled representation, as seen from the observerposition. In prior art methods, the holographic transformation andencoding process can only begin when the results (the two memorysections) are available in their entirety, as access to both memorysections is required for this. This leads to a time delay of one videoframe. Such a delay time can be crucial in some interactiveapplications, such as in gaming devices. If the delay time is too long,the reaction time available for the player's activities may be toobrief, so that the player will fail to perform some actions whichotherwise could have been performed. A delay time of one frame, which isno less than about 17 ms in 60 Hz display devices, may be critical infast games. Because holographic displays will only find marketacceptance if there are applications for them, target groups such asvideo game players should be included.

Three dimensional holographic imaging may provide advantages in militaryapplications, as being able to view the enemy, or other information suchas terrain information, in three dimensions may improve combateffectiveness over two dimensional data display. The above time delaymay lead to service personnel death or injury, or damage to or thedestruction of expensive military equipment, if the display is appliedin military applications during combat operations. Therefore reducingthe time delay may improve the effectiveness of three dimensionalholographic imaging in military applications.

In order to reduce the delay time, there is no need to wait until theentire colour and Z-buffer maps are available. Instead the holographiccalculations will be executed immediately as soon as one point in spaceis available after having been processed by the 3D pipeline.Consequently, it can be seen that the 3D pipeline may be extended by aholographic pipeline.

The calculation time for the holographic transformation and encodingpreferably should not exceed the time needed for the calculation of a 3Dpoint by the 3D pipeline, because otherwise further time lags will begenerated. This concept is readily enabled on the basis ofsub-holograms, because in that case only the necessary pieces ofinformation need to be processed. To appreciate this, consider that ifthe holographic transformations were applied from one single 3D point inspace to the entire size of a hologram or SLM, an additionalcomputational load by a factor of 1,000 or more could be the result.Real-time calculations would then probably become impossible usingcurrently available computational hardware. The concept of asub-hologram is shown in FIG. 8 and its associated description. FIG. 18illustrates the preferred use of sub-holograms in the present example ofan implementation. Because the sub-holograms are smaller than the SLM,each can be calculated more quickly than a single hologram which spansthe entire SLM. Furthermore, the sub-holograms may be calculated insequence, which strongly reduces the time delay compared to the case ofthe calculation of a hologram which spans the entire SLM, which can onlybe performed when an entire frame of image data has been received. Whencomparing the two FIGS. 18A and 18B, it can be noticed that thecomputational load for computing each object point is much smaller ifusing sub-holograms, because of the smaller number of cells in asub-hologram compared to the whole SLM.

In some examples of an implementation, the sub-holograms of points whosepositions are closest to the observer (FIG. 16) are stored in asub-hologram buffer. The 3D pipeline data for each cluster is sent tothe corresponding cluster in the display (FIG. 17); the description fromhere focuses on the implementation at the level of a single cluster.Data on the VOW size and VOW direction and distance from the SLM aresupplied to the cluster as inputs to the calculation (FIG. 17). Eachcluster of the display has its own look-up table for storing theencoding of the sub-holograms which it displays, which may be one ormore sub-holograms. If a new point is generated which is even closer tothe observer, the sub-hologram corresponding to that point (SH_(n)) willbe calculated (see FIG. 17), i.e. the holographic transformation isperformed after the dimensions of the sub-hologram have been determined.Then, the content of the cluster of the SLM cannot simply be overwrittenby the sub-hologram, because an SLM cell may contain information fromseveral sub-holograms. This is why a look-up table is searched for anentry of the sub-hologram (SH_(n-1)) at the position xy, which is alsodisplayed on the cluster of the SLM at the time. After having read thecontent of the SH from the LUT, the difference between the currentlydisplayed (SH_(n-1)) and the new SH (SH_(n)) is calculated (see FIG.17).

In the case where a 3D point in space, which is even closer to theobserver than the previous one, will be calculated at the position xylater, this SH_(n) is written to the LUT instead of the old SH_(n-1)(see FIG. 17). Now, the difference SH_(D) will be added to the values inthe SLM, which are stored in a frame buffer. This process is followed bythe encoding and possible corrections (see FIG. 17).

The fact that the display device (SLM) provides its configurationinformation (e.g. type resolution) to the computing unit (see FIG. 17)means that the connection of any holographic display device (SLM) willbe possible. Such devices may differ in size, number of cells or eventhe type of encoding. This solution is thus not restricted to aparticular type of SLM.

G. Hologram Display with Calculation on the Same Substrate, with RandomAddressing of Holographic Displays

The implementation of part A may be implemented using prior art methodsfor performing the holographic calculations. Alternatively, theimplementation of part A may be implemented using a method whichprovides an improved process for performing the holographiccalculations. An example of the method, which provides an improvedprocess for performing the holographic calculations, is as follows, butmany other examples will be obvious to those skilled in the art.

An object of the implementation is to reduce the amount of data to betransferred from a content generation module (e.g. a graphics card) tothe visualisation module (i.e. the holographic display) by takingadvantage of features of sub-holograms in the application.

The transfer of image data from the content generation units (e.g. agraphics card) to the visualisation module (e.g. an LCD or cathode raytube (CRT) monitor) in the prior art is such that the entire content ofan image is output line by line from top to bottom, as with conventionaltube monitors. With high definition television (HDTV) resolutions up to3840×2400 pixels (IBM® Berta Display→now IIIAMA etc. described at e.g.http://www.pcmag.com/article2/0,1895,2038797,00.asp), this does not posea problem, because the required amount of data can be transferred fastenough through standardised interfaces, such as Digital Visual Interface(DVI) or High-Definition Multimedia Interface (HDMI).

However, ideal holographic display devices require a much higher numberof pixels in order to generate in the observer plane a virtual observerwindow (VOW) which measures one or more centimetres across, in contrastto about 5 mm across in a more primitive device. A large VOW is verybeneficial, because the larger it is the more robust is the holographicdisplay device in terms of reliability during commercial use. This isbecause the demands made on other components in tracked holographicdisplays, such as the tracking system or the position finder, whichtrack the positions of the viewer's eyes with respect to the display,will be much lower in such cases. Alternatively, where the device doesnot implement tracking, the tolerance to small movements of the viewer'shead is improved if the size of the VOW is increased.

An object of the implementation is to reduce the amount of data to betransferred from a content generation module to the visualisation modulein a holographic display in which all or at least some of theholographic calculations take place in the pixel matrix.

During the above described prior art data transfer all information istransferred, including those pieces of information which do not changefrom one frame to the next frame. Because a hologram reconstructs pointsin a three-dimensional space, it is sufficient to know which points havechanged compared to the previous frame. Only those points will beconsidered in the following process (see FIG. 19).

A single object point is created by a sub-hologram SH, whose sizedepends on the observer position. Because an SLM cell may contain notjust the information of one sub-hologram, but the information of severalsub-holograms, the difference between the SH of the old point at theposition xyz and the SH of the new point at the same position xyz shouldbe calculated. This differential sub-hologram SHD may then be re-encodedon the SLM in this example of an implementation.

The set of circuitry inside or outside the display receives 3D imagedata, which consists of a colour or intensity map and a Z buffer, on aframe by frame basis. The difference between successive frames iscomputed, as shown schematically in FIG. 20. Following this, updateddisplay data is sent to the holographic transformation units of thedisplay, in the form of image difference data. As shown in FIG. 20, eachholographic transformation unit is sent 3D difference point image datawhich is relevant to the reconstruction point or points it serves toencode on the SLM. If there is no difference, or negligible difference,between display data for successive frames at a given cluster, then nodata need be sent to the holographic transformation unit: this can speedup the effective SLM updating rate of the display system. The part ofthe system which creates the SHDs may be termed the “content creationmodule” and may consist of computing functions and a graphics card. Thesub-hologram is then sent to each cluster. The first task that thecluster performs is to process the information received by separatingthe hologram data and the data regarding the size and position of SHDs.The cluster's task includes writing the SHD into the appropriate RAMcells so that the SH will be displayed correctly at the proper SLMposition and with the correct size.

In addition to the sub-hologram SH_(D) (or alternatively the SH of thenew frame), the size of the sub-hologram in pixels and its positionwithin the display cluster may be specified. Within the holographicdisplay cluster (shown for example in FIG. 20) there is a splitter,which splits the calculated hologram display data into sub-hologram dataand size and position information. The two latter values aim to computethe address range of the sub-hologram in the RAM, so that the data ofthe sub-hologram SH or SH_(D) are written to the correct SLM cellswithin the cluster.

Common SLMs are active matrix displays whose cells should be refreshedcontinuously in order not to lose information. If only new contents werewritten to the SLM, information in other regions would be lost (e.g. seeFIG. 19: the four black dots therein would no longer appear). For thisreason a special random access memory (RAM) may be used where only thenew SH or SH_(D)s are written on the input side while on the output sidethe entire memory is read line by line and the information is written tothe SLM. Dual-port RAMs or other memory systems which permitsimultaneous reading and writing operations, as described above, to beperformed may be used for this purpose.

Which points are to be transferred, i.e. depending on the changes in the3D scene, will be determined in the content generation unit. The actionto minimise the data stream is thus performed before the data aretransferred to the holographic display device. The information can betransferred in any order, because the sub-holograms are supplementedwith additional information, as described above. This is substantiallydifferent from line-by-line data transfer as practiced in visualisationsystems of the prior art.

On the client's side, i.e. where the content is generated, a decisionwhether or not the data are to be transferred is made before the datatransfer is started, as described in the implementation. If the contenthas changed completely, as is the case after interruptions or a completechange of the scene to be displayed, very many sub-holograms whichcorrespond with the 3D object points should be transferred. Typically,it can be said that the higher the resolution of an SLM, the greater theadvantage in transferring sub-holograms instead of transferring theentire hologram.

H. Display with Computational Function in the Pixel Space

In a further example of an implementation, a display is used to displayimage data, which may be normal display data or may be hologram displaydata which has been computed based on intensity map and depth map data.Inherent problems with displays of the prior art is that they requirecircuitry which is not implemented on the same substrate as the displaycircuitry. This additional circuitry must be implemented on a separatesubstrate to the display substrate. This leads to undesirable propertiessuch as greater device volume and weight. Consumers are constantlydemanding display devices which are smaller, slimmer, or lighter. Theseproblems such as greater device volume and weight may be reduced if anapproach such as the approach of FIG. 25 is adopted. The delay indisplaying any data which has been calculated for display by thecomputational units may be reduced if the computational units aredisposed close to the pixels of the display. Such a reduced delay may bebeneficial in applications such as high speed game devices, or indevices for military applications where improved device performancespeed may lead to a military advantage.

In the display of FIG. 25, computational functions are performed atdisplay clusters which are situated in between the display pixels of thedisplay, or next to the display pixels of the display. The space inwhich the computational functions are performed is on the same substrateas the display's substrate. In FIG. 25, the TFTs for the computationperform the computational functions. Other examples will be obvious tothose skilled in the art.

I. Occlusion

In computer graphics, the term “occlusion” is used to describe themanner in which an object closer to the view masks (or occludes) anobject further away from the view. In the graphics pipeline for 2Ddisplays one implements a form of occlusion culling to remove hiddensurfaces before shading and rasterizing take place. Here in the contextof holograms, the implementation of occlusion involves ensuring thatobject points closer to the virtual observer window mask object pointsfurther away from the virtual observer window, along the same line ofsight.

An example of the desired occlusion behaviour for a holographic displayis given in FIG. 29. In FIG. 29, from the eye position shown, it shouldnot be possible to see the thick side of the cube, because it isoccluded by the side of the cube which is closest to the viewer. If theVOW were several times the size of the eye pupil, the viewer could lookat the cube from a different direction so as to be able to see the thickside of the cube. But with a simple implementation of occlusion, thethick side of the cube would not have been encoded on the SLM, so evenif the viewer were to change the viewing direction, the viewer would notsee the thick side of the cube, because it was not encoded on the SLM.

In FIG. 30, the viewer looks at the cube from a different direction tothat shown in FIG. 29 so as to be able to see the thick side of thecube. But with a simple implementation of occlusion, if occlusion hasnot been implemented for the case of FIG. 29, the thick side of the cubewould not have been encoded on the SLM, so the viewer in FIG. 30 doesnot see the thick side of the cube, because it was not encoded on theSLM: there are no reconstructed object points for the thick side of thecube in FIG. 29, hence there are no reconstructed object points for thethick side of the cube in FIG. 30.

One solution to the problem shown in FIG. 30 is to separate the VOW intotwo or more segments. Object points are then reconstructed for each VOWsegment. The size of each VOW segment is preferably about the same sizeas the human eye pupil size.

In FIG. 31, from eye position 1 the viewer will see object point 1 butnot the occluded object point 2. From eye position 2, the viewer willsee the object point 2, but not object point 1 which cannot be seen fromthat position and viewing direction. Therefore from eye position 2 theviewer can see object point 2 which is occluded by object point 1 whenviewing from eye position 1. Object point 1 and object point 2 areencoded respectively in subhologram 1 and subhologram 2.

However, in FIG. 32 object point 1 and object point 2 which arecoincident can be seen from both eye position 1 and eye position 2,because they are encoded respectively in subhologram 1 and subhologram2.

Alternatively occlusion may be performed at the stage that the depth mapand intensity map is constructed. In this case, preferably one depth mapand intensity map pair should be constructed for each eye i.e. for eachvirtual observer window.

In the example of an implementation included here, occlusion isimplemented using calculations which are performed by circuitry which ispresent in the space of the pixel matrix. Such circuitry may includeTFTs. Occlusion may also be implemented using calculations which areperformed by circuitry which is present on the same substrate as thepixel matrix, but the circuitry is outside the pixel matrix.

J. Graphics Card Functionalities

A Graphics Processing Unit or GPU (also occasionally called VisualProcessing Unit or VPU) is a dedicated graphics rendering device for apersonal computer, workstation, or game console. Modern GPUs are veryefficient at manipulating and displaying computer graphics, and theirhighly parallel structure makes them more effective than typical CPUsfor a range of complex algorithms.

Modern graphics processing units (GPU)s use most of their transistors todo calculations related to 3D computer graphics. They were initiallyused to accelerate the memory-intensive work of texture mapping andrendering polygons, later adding units to accelerate geometriccalculations such as translating vertices into different coordinatesystems. Recent developments in GPUs include support for programmableshaders which can manipulate vertices and textures with many of the sameoperations supported by CPUs, oversampling and interpolation techniquesto reduce aliasing, and very high-precision color spaces.

In addition to the 3D hardware, today's GPUs include basic 2Dacceleration and frame buffer capabilities (usually with a VideoGraphics Array (VGA) compatibility mode). In addition, most GPUs madesince 1995 support the YUV color space and hardware overlays (importantfor digital video playback), and many GPUs made since 2000 supportMoving Picture Experts Group (MPEG) primitives such as motioncompensation and Inverse Discrete Cosine Transform (iDCT). Recentgraphics cards even decode high-definition video on the card, takingsome load off the central processing unit. The YUV color space modeldefines a color space in terms of one luma and two chrominancecomponents. The YUV color model is used in the PAL, NTSC, and SECAMcomposite color video standards.

Here in the context of holograms, the implementation of graphics cardfunctionalities involves ensuring that the above describedfunctionalities are implemented when the holograms are calculated fordisplay, where the display may perform all the holographic calculationsin the space of the pixel matrix, or at least some of the holographiccalculations in the space of the pixel matrix. For example, thisincludes implementing shaders which can manipulate vertices and textureswith many of the same operations supported by CPUs, oversampling andinterpolation techniques to reduce aliasing, the use of veryhigh-precision color spaces, to accelerate the memory-intensive work oftexture mapping and rendering polygons, to accelerate geometriccalculations such as translating vertices into different coordinatesystems, and performing computations involving matrix and vectoroperations. For calculating holograms, the highly parallel structure ofGPUs makes them more effective than typical CPUs for a range of complexalgorithms. Alternatively, the holographic display may be one in whichno holographic calculations are performed in the space of the pixelmatrix.

Here in the context of holograms, the implementation of graphics cardfunctionalities may involve using a 3D-rendering pipeline which isimplemented by TFTs in the space of the pixel matrix, or outside thepixel matrix but on the same substrate as the pixel matrix. In otherwords the functionality of a 3D-rendering pipeline, such as implementingshader functionalities, is shifted from the graphics cards used in theprior art to the TFTs situated within a LC-panel.

Alternatively, the holographic display may be one in which noholographic calculations are performed in the space of the pixel matrix.Alternatively still, the holographic display may be one in which noholographic calculations are performed in the space of the pixel matrix,but the holographic calculations may be performed using circuitry whichis present on the same substrate as the pixel matrix.

K. 2D-3D Conversion

In one example of 2D-3D conversion, a first image and a second imagewhich form a pair of stereoscopic images, are sent to the display devicewith all or at least some holographic calculation performed in the spaceof the pixels or elsewhere on the substrate of the pixels. The 2D-3Dconversion calculation may take place in circuitry in the space of thepixel matrix or elsewhere on the substrate of the pixels, or it may takeplace in circuitry which generates the depth map and colour intensitymap to be sent to the display, or it may take place in circuitryelsewhere, as would be clear to one skilled in the art. The secondtransmitted image may be the difference image between the twostereoscopic images, as a difference image will typically require lessdata than a complete image. If a three dimensional video display is inprogress, the first image may itself be expressed as the differencebetween the present image and the image from one timestep earlier.Similarly the second image may be expressed as the difference betweenthe present image and the image from one timestep earlier. The displaydevice may then calculate a two dimensional (2D) image, with itscorresponding depth map, from the data received, using calculationprocedures for converting between 2D and three dimensional (3D) imagesknown in the art. In the case of a colour image, three component 2Dimages in the three primary colours are required, together with theircorresponding depth maps. The data corresponding to the 2D images anddepth maps may then be processed by the device to display a holographicimage. The device encodes the holograms in its SLM. To make efficientuse of transmission bandwidth, the data transmitted within this systemmay be subjected to known compression procedures, with correspondingdecompression being performed at the display device.

The circuitry which performs the 2D-3D conversion may have access to alibrary containing a set of known 3D shapes, to which it may try tomatch its calculated 3D data, or it may have access to a librarycontaining a set of known 2D profiles to which it may try to matchincoming 2D image data. If a good match can be found with respect to aknown shape, this may speed up calculation processes, as 2D or 3D imagesmay then be expressed relative to a known shape. Libraries of 3D shapesmay be provided such as the face or body shapes of a set of sports starssuch as leading tennis players or soccer players, and the shapes of allor parts of leading sports venues such as famous tennis courts or famoussoccer grounds. For example, a 3D image of a person's face may beexpressed as being one to which the display device has access, plus achange to the facial expression which may be a smile or a frown forexample, plus some change in the hair length as the hair may have grownor been cut since the stored data was obtained, for example. The data towhich the display device has access may be updated by the display deviceif a persistent set of differences emerges such that it is clear thatthe data to which the display device has access has become out of date,e.g. the person's hair length has been changed significantly and on along term basis. If the calculation circuitry encounters a 2D or 3Dimage to which no good match can be found in the records to which it hasaccess, it may add the new shape to the set of records.

2D-3D image conversion may also be performed based on a single,non-autostereoscopic 2D image using procedures known in the art forperforming such conversions. The 3D image data (depth map and colourmap) may then be sent to the display for holographic image calculationand display.

The above 2D-3D conversions may be used for data which is used fordisplay on a holographic display in which all the holographiccalculations take place in circuitry in the space of the pixel matrix,or at least some of the holographic calculations take place in circuitryin the space of the pixel matrix, or elsewhere on the substrate of thepixels.

L. Conferencing (3D Skype™)

From EU Community Trade Mark application E3660065, Skype™ is known forproviding voice over Internet (VoIP) peer-to-peer communications, andfile sharing, and instant messaging services over a global network;providing communication services, file sharing and instant messagingservices over a computer network.

From EU Community Trade Mark application E4521084, Skype™ is known forproviding computer services and software development for others, namely,design of computer software and hardware for use in telecommunicationsand voice over internet protocol (VoIP) applications, data transmissionand instant messaging services; creating and maintaining web sites forothers; hosting web sites of others on a computer server for a globalcomputer network; installation and maintenance of computer software;providing temporary use of online, non-downloadable computer softwarethat allows subscribers to utilize VoIP communication services;providing online software for downloading by others that allowssubscribers to utilize VoIP communication services.

From UK Trade Mark 2358090, Skype™ is known for providing internetaccess, portal and caching services; telecommunications andtelecommunications services; Internet Protocol (“IP”) services; Voiceover Internet Protocol (“VoIP”) services; email and Internetcommunications services; telecommunications services via a third party;Internet Protocol (“IP”) to numeric telephone number and numerictelephone number to “IP” mapping systems and databases; domains anddomain database systems; leasing of access time to computer databasesprovided by Internet Services Providers.

Any of the above may be provided in conjunction with a holographicdisplay which may perform all holographic calculations using circuitryin the space of the pixel matrix, or at least some holographiccalculations using circuitry in the space of the pixel matrix, exceptthat where Skype™ provides VoIP, here there is provided a voice andholographic image over internet protocol (VHIOIP). In one case, theabove described procedures are performed by TFTs within the LC-panel.Alternatively, any of the above may be provided in conjunction with aholographic display which does not perform holographic calculations inthe space of the pixel matrix, except that where Skype™ provides VoIP,here there is provided a voice and holographic image over internetprotocol (VHIOIP). Alternatively still, any of the above may be providedin conjunction with a holographic display which does not performholographic calculations in the space of the pixel matrix, but whichperforms holographic calculations using circuitry on the same substrateas the pixel matrix, except that where Skype™ provides VoIP, here thereis provided a voice and holographic image over internet protocol(VHIOIP). Alternatively still, any of the above may be provided inconjunction with any holographic display, except that where Skype™provides VoIP, here there is provided a voice and holographic image overinternet protocol (VHIOIP).

Alternatively, any of the above may be provided in conjunction with aholographic display which does not perform holographic calculations inthe space of the pixel matrix, except that where Skype™ provides VoIP,here there is provided a voice and holographic image over internetprotocol (VHIOIP).

In the above, VHIOIP may be provided in the form of voice and videoholographic image over internet protocol (VVHIOIP). The VHIOIP orVVHIOIP may be provided in real time or in quasi-real-time, and theseinternet protocols may enable real-time or quasi-real-time videoholographic communication between two human beings who each use aholographic display.

M. Encoding Compensations

In conventional photography, exposure compensation is a technique tocompensate a calculated or planned exposure level against other factorswhich may render a sub-optimal image. These factors may includevariations within a camera system, filters, non-standard processing, orintended under or overexposure. Cinematographers may also apply exposurecompensation for changes in shutter angle or film speed, among otherfactors. In photography, some cameras include this as a feature to allowthe user to adjust the automatically calculated exposure. Compensationcan be applied both positively (additional exposure) and negatively(reduced exposure) in steps, normally in third or half f-stop incrementsup to a maximum of normally two or three stops in either direction.

In optics, the f-number of an optical system expresses the diameter ofthe entrance pupil in terms of the effective focal length of the lens.On a camera, the f-number is usually adjusted in discrete steps, knownas f-stops. Each “stop” is marked with its corresponding f-number, andrepresents a halving of the light intensity from the previous stop. Thiscorresponds to a decrease of the pupil and aperture diameters by afactor of the square root of 2, and hence a halving of the area of thepupil.

Exposure compensation is employed when the user knows that the camera'sautomatic exposure calculations will result in an undesirable exposure.A scene that is predominantly light tones will often be underexposed,while a dark-toned scene will be overexposed. An experiencedphotographer will have gained a sense of when this will happen and howmuch compensation to apply to get a perfectly exposed photograph.

Any of the above may be provided in conjunction with a holographicdisplay which performs all holographic calculations on the samesubstrate as the pixel matrix, or at least some holographic calculationson the same substrate as the pixel matrix. Any of the above may beprovided in conjunction with a holographic display which performs allholographic calculations on the same substrate as the pixel matrix, orat least some holographic calculations in the space of the pixel matrix.Alternatively, any of the above may be provided in conjunction with anyholographic display. Compensation may be applied to the holographicimage data at or before the encoding step, to provide an image whichwill be easier to view i.e. which the typical observer will find to havebeen exposed correctly, and not to have been either under-exposed orover-exposed.

N. Eye Tracking

Holographic devices may use eye tracking, for one or more viewers. Thisis particularly advantageous when the viewing window size for each eyeis small, such as being only a few millimetres in lateral extent.Preferably a position finder is used to track the eyes of users inseveral steps:

-   -   1) limiting the search range by detecting the user's face    -   2) limiting the tracking range by detecting the eyes    -   3) tracking the eyes

The calculation module for performing the eye position identificationfunction is provided with a stereo image pair as supplied by a stereocamera. After having used the algorithms of the module, the modulereturns the x-, y-, and z-coordinates of each eye relative to a fixedpoint, such as the centre of the SLM. Such coordinates can, for example,be transmitted by a serial interface. The computation required in orderto perform this procedure may be performed by circuitry, such as TFTs,situated on the same substrate as the pixels of the display, includingcircuitry situated within the pixel matrix.

In order to track the eye of a viewer, the holographic encoding on theSLM panel may be displaced in the x- and/or y-directions i.e. in theplane of the panel. Dependent on the type of holographic encoding methodused (e.g., 1D-encoding), it may be preferable that tracking of eyes inone lateral direction should be carried out by displacing the entireholographic encoding content on the SLM in the x- or y-direction. Priorto holographic encoding of the SLM, the calculation module calculatesthe offset of the hologram data in relation to the SLM in the x- ory-direction. As input, the x, y and z-coordinates of a viewer's eye areprovided.

In order to track the eye of a viewer, the holographic encoding on theSLM panel may be displaced in the x- and/or y-directions i.e. in theplane of the panel. Tracking can also be carried out such that the lightsources that coherently illuminate the SLM are moved in synchronism withposition changes of the viewer. Either the light sources that emit lightare moved, or coherent light is generated in that point light sources orline light sources with very narrow openings are illuminated bynon-coherent light. The light passing through such openings isconsidered to be coherent. If the light sources are created by thepixels of an LC-display, they are addressable and can be adapted to thepositions of the viewer(s) in real time.

O. Aberration Correction

Within some types of holographic display, aberration correction is thecorrection of aberrations caused by the lenses in a lenticular array, orin a 2D-lens array, that performs the Fourier transformation. Aberrationeffects depend on the angle between the light propagation direction tothe viewer and the optic axis, and may be corrected dynamically throughthe encoding of the spatial light modulator. The correction algorithmmay be performed in parallel, and independently, of the holographiccalculation up to the step where the sum-hologram is generated. Afterthat step the sum-hologram and the aberration correction map may bemodulated together.

The aberration correction algorithms can implemented analytically orusing look-up tables (LUT) as well. Preferably the resulting hologramcalculation values are modulated by complex multiplication only afterthe sum hologram is available. An example of the implementation ofaberration correction is given in FIG. 33. In FIG. 33 the aberrationcorrection is implemented using circuitry in the space of the pixelmatrix. However in other cases the aberration correction may beimplemented using circuitry outside the space of the pixel matrix, buton the same substrate as the pixel matrix.

P. Speckle Correction

Within some types of holographic display, speckle correction is thereduction or elimination of speckle caused by too large a degree ofoptical coherence between different areas on the display. Speckleeffects may be corrected dynamically through the encoding of the spatiallight modulator. The correction algorithm may be performed in parallel,and independently, of the holographic calculation up to the step wherethe sum-hologram is generated. After that step the sum-hologram and thespeckle correction map may be modulated together.

The speckle correction algorithms can implemented analytically or usinglook-up tables (LUT) as well. Preferably the resulting hologramcalculation values are modulated by complex multiplication only afterthe sum hologram is available. An example of the implementation ofspeckle correction is given in FIG. 33. In FIG. 33 the specklecorrection is implemented using circuitry in the space of the pixelmatrix. However, the speckle correction may be implemented usingcircuitry outside the space of the pixel matrix, but on the samesubstrate as the pixel matrix.

Q. Decryption in Digital Rights Management (DRM) for a HolographicDisplay

Content data supplied to a holographic display may be protected by DRMi.e. encrypted content data is received by the display. High-bandwidthDigital Content Protection (HDCP) is a common standard to implement DRMfor 2D displays. The High-Definition Multimedia Interface (HDMI)receiver with the HDCP decryption is normally located on the printedcircuit board (PCB) of the 2D display's electronics. One of thefundamental weaknesses of conventional systems is that the transfer ofimage data from the display electronics to the panel is normally afterdecryption. So it is possible to capture the decrypted data by makingelectrical connections to the data transmission circuitry for the panel.

In an example of an implementation, decryption and hologram calculationare executed using circuitry within the pixel matrix. In a furtherexample of an implementation, decryption and hologram calculation areexecuted in a distributed sense using circuitry which is distributedwithin the pixel matrix. Therefore there is no single place on the panelfrom which all decrypted data can be captured. If different decryptionkeys are used for different areas of the panel, the extraction of thedecryption keys will become more difficult. Because there are noconnectors on the panel from which to extract the decrypted data fromthe panel, those wishing to circumvent DRM must know the circuit diagramand several TFT transistors must be connected to which are widelyseparated across the working display in order to access decrypted data.This contributes to improved DRM protection.

A further example of an implementation is that decryption and hologramcalculation is executed using circuitry which is on the substrate of thepixel matrix, including the case where the circuitry is outside thepixel matrix. A further example of an implementation is that decryptionand hologram calculation is executed in a distributed sense usingcircuitry which is distributed across the substrate of the pixel matrix,including the case where the circuitry is outside the pixel matrix.

R. Decryption in Digital Rights Management (DRM) for a 2D Display

Content data supplied to a 2D display may be protected by DRM i.e.encrypted content data is received by the display. High-bandwidthDigital Content Protection (HDCP) is a common standard to implement DRMfor 2D displays. The High-Definition Multimedia Interface (HDMI)receiver with the HDCP decryption is normally located on the printedcircuit board (PCB) of the 2D display's electronics. One of thefundamental weaknesses of conventional systems is that the transfer ofimage data from the display electronics to the panel is normally afterdecryption. So it is possible to capture the decrypted data by makingelectrical connections to the data transmission circuitry for the panel.

In an example of an implementation, decryption is executed in adistributed sense using circuitry which is distributed across the SLMpanel. Therefore there is no single place on the panel from which alldecrypted data can be captured. If different decryption keys are usedfor different areas of the panel, the extraction of the decryption keyswill become more difficult. Because there are no connectors on the panelfrom which to extract the decrypted data from the panel, those wishingto circumvent DRM must know the circuit diagram and several TFTtransistors must be connected to which are widely separated across theworking display in order to access decrypted data. This contributes toimproved DRM protection.

In a further example of an implementation, there is a 2D display devicein which decryption calculations are executed using circuitry which isin a single area of the display substrate, which may be inside the pixelmatrix or outside the pixel matrix. Such circuitry is harder to accessthan circuitry which is on the PCB of the display. This contributes toimproved DRM protection.

S. Software Application Implemented in Hardware, Hard-Wired into aDisplay

In principle many pieces of computer software may also be implementedindependently using computer hardware. In an example of animplementation, an application which may be implemented using softwareis instead implemented in hardware using circuitry which is distributedacross the substrate of an SLM panel. The circuitry may be within thepixel matrix, or it may be on the same substrate as the pixel matrix butoutside the pixel matrix. The SLM panel may be that for a holographicdisplay, or for a 2D display.

T. Variable Beam Deflection with Microsprisms

For a holographic display, the viewer's or viewers' eye positions may betracked, variable beam deflection to the viewer's or viewers' eyepositions being performed using a microprism array which enablescontrollable deflection of optical beams. The controllable deflectionmay be continuously variable. The tracking is performed by a positiondetection and tracking system. The properties of the prisms can becontrolled in such a way that they deflect light in either one or twodimensions. Two dimensional deflection could be obtained by using twomicroprism arrays in series, for example, with the longitudinal axes ofthe prisms in one array being disposed at a significant angle, such asabout 90°, to the longitudinal axes of the prisms in the other array.Such a geometry, for a different application, is described in e.g. U.S.Pat. No. 4,542,449 which is incorporated here by reference. FIG. 34shows light being deflected by a smaller or by a larger angle dependingon the properties of the prisms. The prisms may be Micro Liquid Prisms[e.g. as described in “Agile wide-angle beam steering withelectrowetting microprisms” Heikenfeld et al., Optics Express 14, pp.6557-6563 (2006), which is incorporated herein by reference], for whichthe deflection angles can be varied according to the applied charge, orother known prism arrays which enable controllable deflection of opticalbeams.

As can be seen in FIG. 34, parallel light rays passing through the SLMand the prism mask are deflected according to the properties of theprisms. An advantage of this procedure is that optical effects likeaberrations of lenses can be reduced prior to light passing through theprism. This method is suitable for placing the VOWs at the viewer's orviewers' eyes. In an alternative example, a focussing means such as aFourier lens array placed before or after the prism array will assist toconverge the light rays into the VOW.

When an observer changes his position, the deflection angle of theprisms may be adjusted accordingly, such as by adjusting the appliedvoltage on the micro liquid prism array. The deflection angle may becontinuously variable. The prisms need not all have the same deflectionangle. It is also additionally possible to control each prismindividually, so that each may have a different deflection angle, e.g.for Z Tracking i.e. enabling the light rays exiting the prism array toconverge somewhat at the VOW, as the distance of the VOW from thedisplay may vary as the viewer moves closer to the display or furtheraway from the display.

The prism angle calculation can be performed taking into account theuser position. The prism angle calculation can be performed incomputational circuitry on either the SLM's substrate, such as that thatreconstructs the object points, or using computational circuitry placedon the substrate of the prism array. An independent substrate for theprism array is not needed if the substrate of the SLM can also be usedas the substrate for the prism array.

A communications interface between the position finder and the SLM isnecessary: for instance this could be a serial interface.

If the computational circuitry for calculating the prism arraydeflection angles is not on the substrate of the prism array but is onthe substrate of the SLM, then a data connection is necessary betweenboth substrates so the electrodes of the prism array can be controlledusing the results of the calculation.

In addition to the calculation for controlling the prisms, one has toapply a phase correction to compensate for phase “jumps” (or phasediscontinuities) introduced by the prism array. Otherwise the prismarray would behave like a blazed grating i.e. the portions of thewavefront passing through different prisms have different optical pathlengths to the VOW, hence they will behave like a grating, while thechange of the prism angle affects the amount of energy distributed tothe different diffraction orders. This phase correction may be performedby the SLM in addition to its function of hologram encoding. The lightpassing through both components, i.e. the prism array and the SLM,undergoes a complex multiplication by the functions of each component.The corrected phase map includes the phase correction required for themicro prism array: the hologram is encoded with the values representingthe SLM cell states which reconstruct object points, including the phasecorrection terms.

The above may also be applied to the case where the holographic image isgenerated in a projection-type apparatus, where the projection involvesimaging a SLM onto the prism array while the reconstruction of thedesired 3D scene occurs in front of the VOW, thereby creating projectionapparatus equivalent to those known in the art. The calculations andapparatus required are similar to those described above, as would beappreciated by one skilled in the art. The deflection angles for theprisms in the prism array, and the according phase compensation tocorrect for phase discontinuities, have to be calculated. The phasecompensation for the prism array can be either provided when imaging theSLM onto the prism array or separately by an additional SLM placed nearto the prism array. The SLM can be transmissive with the prism arrayreflective, or the SLM can be reflective with the prism arraytransmissive, in order to enable projection, as would be appreciated byone skilled in the art.

Micro Liquid Prisms are described e.g. in “Agile wide-angle beamsteering with electrowetting microprisms” Heikenfeld et al., OpticsExpress 14, pp. 6557-6563 (2006), which is incorporated herein byreference. The technology is known as “electrowetting” or “e-wetting”.In this technology, the contact angle formed by an interface between atransparent conducting liquid and another fluid (e.g. air) with anelectrode coated with a hydrophobic insulator is a function of thevoltage difference applied to the electrode with respect to thetransparent conducting liquid. Independent control of the voltagesapplied to two electrodes each covered with a hydrophobic insulator,each electrode forming a side-wall of an e-wetting cell opposite theother side wall formed by the other electrode, permits control of theangle by which an optical beam is steered as it traverses the cell.Other configurations for achieving optical beam steering byelectrowetting prisms will be obvious to those skilled in the art. Theoptical beam deflection angle is controlled by using variable voltagedifferences applied to different electrodes located on different sidesof each of an array of electrowetting cells.

First Outline Manufacturing Process

In the basic structure of the thin film semiconductor display device ofan implementation, there is provided a display part with circuitrydisposed in between the pixels of the display part, or elsewhere on thesubstrate, for performing calculations associated with the display ofdata on the display part of the device. The display part, and thecalculation-performing circuitry within the display part or elsewhere onthe substrate, are formed integrally on the substrate. Further circuitryfor driving the display part may be formed peripherally to the displaypart, but integrated on the same substrate.

The TFT circuitry for operating the spatial modulator, and furthercircuitry such as for performing logic operations, may be created on asubstrate by a method such as is described in the following, which issimilar to a method described in U.S. Pat. No. 6,153,893 for fabricatinga different device structure; U.S. Pat. No. 6,153,893 is incorporatedherein in its entirety by reference. Other methods will be obvious tothose skilled in the art. The substrate may be a large area substrate,and the substrate may be a suitable type of glass. With glass substratesthe processes which are often used tend to be low temperature processes,at least by the standards of Si device fabrication technology. Processessuch as thermal oxidation of silicon at approximately 1000° C. forproducing device gate insulating layers tend to be incompatible with lowtemperature processes, which would typically be in the temperature rangefrom 350° C. to 700° C.

Pixel electrodes and thin film transistors for switching are arranged ina matrix in the display part. Thin film transistors to constitutecircuit elements are in between the pixels of the display part orelsewhere on the substrate, and optionally in the display driving partwhich may be integrated on the same substrate. The thin film transistormay be a bottom gate type comprising a gate electrode, a polycrystallinesemiconductor layer formed on an insulating layer on the gate electrode,and a high concentration impurity film constituting a source and a drainformed on the polycrystalline semiconductor layer. TFTs for switchingmay have a lightly doped drain (LDD) structure wherein a lowconcentration impurity film is interposed between the polycrystallinesemiconductor layer and the high concentration impurity film.

In a typical implementation, the display part has an upper side partthat includes pixel electrodes, a lower side part that includes TFTs forswitching, and possibly a colour filter layer, a black mask layer and aplanarization layer interposed between the upper and lower sides. Inthis case, the black mask layer contains a metal wiring patternelectrically connected to the high concentration impurity layer for thesource and drain. Also, the pixel electrodes are electrically connectedvia the metal wiring pattern to the high concentration impurity film forthe drain. Alternatively, a colour filter layer can be omitted if abacklight is used with three primary colours which illuminate in atime-multiplexed mode.

A display device with the above described structure can be manufacturedby the following low temperature process. First, gate electrodes areformed on the glass substrate. Next, a semiconductor thin film is formedon an insulating film on the gate electrodes and then the semiconductorthin film is transformed into a polycrystalline layer by laserannealing. A low concentration impurity layer is then selectively formedonly on the polycrystalline layer included in pixel switching, such asthrough the use of a mask layer. Further, a high concentration impuritylayer for sources and drains is formed on the low concentration impurityfilm, and TFTs for switching having a stacked LDD structure are therebyformed. At the same time, TFTs for circuit elements are made by directlyforming a high concentration impurity layer for sources and drains onthe polycrystalline layer included in the circuitry parts, such as forimage display calculation, or for the peripheral driving part.Preferably, laser annealing is performed selectively on the highconcentration impurity layers included in the circuitry parts in orderto reduce the resistance of the polycrystalline semiconductor layer.

After gate electrodes are formed on a glass substrate a semiconductorfilm is formed at low temperature on a gate insulating film on the gateelectrodes. The semiconductor film is then transformed into apolycrystalline layer by laser annealing. Hence it is possible to form apolycrystalline TFT by low temperature processes. The laser used willtypically have a short wavelength so that the laser radiation isstrongly absorbed in Si: an example is an excimer laser, but others areknown. Because the TFT is a bottom gate type, this structure does notreadily suffer adverse influences from impurities such as sodium in theglass substrate. The polycrystalline semiconductor layer used in thedevice region permits one to make the TFT small. In the TFTs for pixelswitching, the LDD structure keeps leakage currents low. If the leakagecurrents were too high, these would be fatal defects in a displaydevice. In the TFTs constituting circuit elements, by contrast,N-channel TFTs and P-channel TFTs can be formed at the same time bysuperposing a high concentration impurity layer on the polycrystallinesemiconductor layer by low temperature processes. Additional laserannealing of the TFTs constituting circuit elements may be performed toincrease the speed of these TFTs. A further structure may be adopted,including a colour filter layer, a black mask layer and a planarizationlayer, to contribute to the attainment of higher pixel density andhigher aperture rates.

The structures which can be made by this manufacturing method are notlimited to TFT structures but can be applied to any known structures.

Second Outline Manufacturing Process

In the basic structure of the thin film semiconductor display device ofan implementation, there is provided a display part with circuitrydisposed in between the pixels of the display part, or elsewhere on thesame substrate, for performing calculations associated with the displayof data on the display part of the device. The display part, and thecalculation-performing circuitry, are formed integrally on thesubstrate. Further circuitry for driving the display part may be formedperipherally to the display part, but integrated on the same substrate.

The TFT circuitry for operating the spatial light modulator, and furthercircuitry such as for performing logic operations, may be created on asubstrate by a method such as is described in the following, which issimilar to the method described in U.S. Pat. No. 6,140,667 forfabricating a different device structure; U.S. Pat. No. 6,140,667 isincorporated herein in its entirety by reference. Other methods will beobvious to those skilled in the art. The type of silicon which can bemade using this manufacturing process is called “continuous grainsilicon” and its electrical characteristics may be similar to those ofmonocrystalline silicon in some respects, or in many respects.

FIGS. 11, 12 and 13 show an outline of the process which may be used toform continuous grain (CG) silicon suitable for use in displays,including use in pixel switching, display driving and logic circuitry.The substrate 1101 may be a large area substrate, and the substrate maybe a suitable type of glass, or quartz. A non-transparent substrate suchas intrinsic polycrystalline silicon or a ceramic could be used in thecase of a display to be used in a reflective geometry only, as in areflective geometry light transmission by the substrate is not anecessary requirement. The substrate has an insulating surface. Film1102 is an amorphous silicon film in which the silicon thickness isbetween 10 nm to 75 nm, which excludes any oxide formed. The film may begrown by low pressure chemical vapour deposition (CVD), or by a plasmaCVD process.

In the following, a process of crystallizing silicon is described, butmany others are known in the art. A mask insulating film 1103 is formed,where openings correspond to the desired positions of CG silicon on thesubstrate. A solution including Ni as a catalyst element forcrystallizing amorphous Si is coated by a spin coating process in whichlayer 1104 is formed. Other catalyst elements such as Co, Fe, Sn, Pb,Pd, Pt, Cu or Au or the like may be used. At the openings in film 1103,the catalyst film 1104 is brought into contact with the amorphous Sifilm 1102. The amorphous Si film 1102 may then be crystallized byannealing at temperatures between 500° C. and 700° C. for between 4 hrand 12 hr, in an inert atmosphere, or in an atmosphere which includeshydrogen or oxygen.

As shown in FIG. 11B, crystallization of the amorphous Si 1102 ispromoted in regions 1105 and 1106 by the Ni catalyst. Horizontal growthregions 1107 and 1108, which grow substantially across the substrate,are formed. Only these horizontal growth regions, such as 1107 and 1108,are used as active layers in TFT devices formed on the substrate.Following completion of annealing, mask layer 1103 is removed from thesubstrate. Patterning is then carried out, as shown in FIG. 11C.Island-like semiconductor layers 1109, 1110 and 1111, which are activelayers, are formed across the substrate. 1109 is an active layer of anN-channel type TFT constituting a complementary metal-oxidesemiconductor (CMOS) circuit, 1110 is an active layer of a P-channeltype TFT constituting a CMOS circuit, and 1111 is an active layer of anN-channel type TFT constituting a pixel matrix circuit.

When the active layers 1109, 1110 and 1111 have been formed, a gateinsulating film 1112 comprising an insulating film including silicon isformed. The thickness of the gate insulating film 1112 may be in therange of 20 nm to 250 nm, and one should allow for some oxidation ofthis film in a later thermal oxidizing step. The film 1112 may be grownusing known gas-phase growth methods.

FIG. 11C shows a heat treatment method for removing the Ni catalystelement. Heating is carried out in the presence of a halogen-containingspecies. Heating is carried out at temperatures between 700° C. and1000° C. for between 0.1 hr and 6 hr. An example is a heat treatment of950° C. for 0.5 hr, in an atmosphere containing HCl with 3 volumepercent (vol %), or more generally between 0.5 vol % and 10 vol %.Oxidation of the silicon in the film can be lowered by mixing in a highconcentration of nitrogen N₂ gas in the atmosphere used. Apart from HCl,other halogen-containing species such as HF, HBr, Cl₂, F₂, Br₂, NF₃ClF₃, BCl₃ and the like may be used. This gettering process serves toremove the Ni catalyst from the film. It seems that this occurs throughvolatile nickel chloride species being formed which desorb into theatmosphere. The thickness of gate insulating film 1112 will tend toincrease during the oxidation process. Regions 1109, 1110 and 1111 arecorrespondingly thinned, which reduces the OFF current in the TFT, andpromotes the field effect mobility amongst other obvious benefits.

Following the above treatment, a heat treatment at 950° C. for 1 hr, ina nitrogen atmosphere improves the quality of the gate insulating film1112 and the quality of the interface between the gate insulating film1112 and regions 1109, 1110 and 1111.

An Al film with 0.2 weight percentage (wt %) of Sc is formed and anelectrode pattern for constituting the prototype of a gate electrode,mentioned below, is formed. This is not illustrated in FIG. 11. Othermaterials suitable for this purpose, such as Ta, W, Mo, or Si can beused. By anodically oxidizing the surface of the pattern, gateelectrodes 1113, 1114 and 1115, and anodized films 1116, 1117 and 1118are formed, as shown in FIG. 11D. In the next step, shown in FIG. 11E,the film 1112 is etched away, such as by using CHF, gas, so that film1112 remains only right beneath the electrodes, such as in positions1119, 1120 and 1121. A resist mask 1122 is used to cover a regionintended for a P-channel type TFT. Impurity ions for n-type material areadded, indicated by the arrows in FIG. 11E, such as by implantation orplasma deposition. The n-type regions 1123, 1124, 1125 and 1126 areformed. Following this process, the resist mask 1122 may be removed, anda resist mask 1127 may be placed over the n-type regions (FIG. 12A). Thep-type regions 1128 and 1129 may then be doped, such as by implantationor plasma deposition. The p-doped regions are the LDD regions. Theresist mask 1127 over the n-type regions may then be removed.

Silicon oxide films are formed on the side walls 1130, 1131 and 1132 viaan etch-back process. The p-type regions are covered by a mask 1133, andn-type dopants are added, to boost the concentration of n-type dopantsin regions not covered by the oxide side walls. The sheet resistance ofthe source/drain region is adjusted to less than 500Ω, preferably toless than 300Ω. A channel forming region 1137 which is intrinsic orsubstantially intrinsic is formed below the gate electrodes. A sourceregion 1138, a drain region 1139, low concentration impurity regions1140 and a channel forming region 1141 of the N-channel TFT constitutingthe pixel matrix circuit are formed (FIG. 12C). In FIG. 12D, the resistmask 1133 is removed and the resist mask 1142 is formed over theN-channel type TFTs. Further p-type impurities are added to boost thep-type dopants' concentration. The resist mask 1142 is then removed andthe impurity ions are activated by heat treatment, such as furnaceannealing, laser annealing or the like. Implantation damage is reducedor eliminated by the heat treatment.

A Ti film 1147 is formed with a thickness between 20 nm and 50 nm and aheat treatment using lamp annealing is carried out. Si in contact withthe Ti film reacts to form titanium silicide, and silicide regions 1148,1149 and 1150 are formed, as shown in FIG. 13A. FIG. 13B showsisland-like patterns 1151, 1152 and 1153 which are formed to prevent thesilicide film regions 1148, 1149 and 1150 from being eliminated fromforming contact holes for connecting source/drain regions and wiring inlater steps.

A Si oxide film is formed with a thickness between 0.3 μm and 1 μm as afirst interlayer insulating film 1154. Contact holes are formed andsource wirings 1155, 1156 and 1157 and drain wirings 1158 and 1159 areformed, as shown in FIG. 13B. An organic resin can be used as a firstlayer insulating film 1154. In FIG. 13C, a second insulating layer 1160is formed on the substrate with a thickness in the range from 0.5 μm to3 μm. Polyimide, acrylic resin, polyamide, polyimide amide or the likeis used as the organic resin film. A black mask 1161 is formed on film1160. A third insulating interlayer film 1162, such as Si oxide, Sinitride, Si oxy-nitride or an organic resin film, or a laminated film ofthese, is formed with a thickness in the range 0.1 μm to 0.3 μm. Contactholes are formed at film 1160 and film 1162, and a pixel electrode 1163is formed with a thickness of 120 nm. An auxiliary capacitance 1164 isformed at a region where the black mask 1161 overlaps the pixelelectrode 1163, as shown in FIG. 13C.

The whole substrate is heated at 350° C. for 1 hr to 2 hrs in a hydrogenatmosphere, which compensates dangling bonds, especially in the activelayers of the films. After these steps, the CMOS circuit on the leftside of FIG. 13C and the pixel matrix circuit on the right side of FIG.13C can be formed on the same substrate, in adjacent positions forexample.

The structures which can be made by this manufacturing method are notlimited to TFT structures but can be applied to any known structures,including bottom-gate TFTs.

Third Outline Manufacturing Process

In the basic structure of the thin film semiconductor display device ofan implementation, there is provided a display part with circuitrydisposed in between the pixels of the display part, or elsewhere on thesame substrate, for performing calculations associated with the displayof data on the display part of the device. The display part, and thecalculation-performing circuitry, are formed integrally on thesubstrate. Further circuitry for driving the display part may be formedperipherally to the display part, but integrated on the same substrate.

The TFT circuitry for operating the spatial light modulator, and furthercircuitry such as for performing logic operations, may be created on asubstrate by a method such as is described in the following, which issimilar to the method described in U.S. Pat. No. 6,759,677 forfabricating a different device structure; U.S. Pat. No. 6,759,677 isincorporated herein in its entirety by reference. Other methods will beobvious to those skilled in the art. The type of semiconductor which canbe made using this manufacturing process is polycrystallinesilicon-germanium and its electrical characteristics may be similar to,or exceed, those of monocrystalline silicon in some respects, or in manyrespects.

This manufacturing process results in circuitry on a single substrate. Agroup of TFTs is produced with polysilicon as the active layer, andwhich control the pixels of the display. Other TFTs are produced whichhave functions such as gate driver circuits, source driver circuits andsignal processing circuits, in which the active layer issilicon-germanium, in order to bring about high speed operation. Ge isadded to the parts of the circuitry requiring high speed operation,whereas poly-Si is used in the circuit section requiring low OFF currentcharacteristics.

An active matrix display device is manufactured having a pixel matrixcircuit, and a driver circuit, which is a CMOS circuit in this example,all formed on an insulating surface of a single substrate. The processis shown in FIG. 6.

As shown in FIG. 6A, a glass substrate 601 is prepared to form thereon alayer of silicon oxide 602. An amorphous silicon film 603 is formed by aplasma CVD method with a thickness of 30 nm. A resist mask 604 isprovided by patterning on the amorphous Si film 603. The resist mask isformed so as to cover the regions to be formed with a TFT group for apixel matrix circuit. The regions to be formed into high speed circuitsare not masked. As shown in FIG. 6B, Ge is added by a technique such asion implantation, plasma doping or laser doping. Ge is added so as tochange the composition of the amorphous Si film to create an averagecomposition of the film of Si_(1-x)Ge_(x), with 0<x<1. If ionimplantation is used, the region 605 to which the Ge is added suffersimplantation damage. The Si_(1-x)Ge_(x) film 605 is in an amorphousstate.

Because the activation energy for bulk diffusion in Ge is lower than inSi, and Ge and Si form a solid solution in each other in the binaryalloy phase diagram for temperatures below the melting point, thepresence of Ge serves to accelerate crystallization of the S_(1-x)Ge_(x)film with respect to the crystallization of a pure Si film. In thisrespect, Ge may be considered to be a catalytic semiconductor withrespect to Si crystallization, such as in laser-induced crystallization.

In FIG. 6C the resist layer 603 is removed and a Ni-containing layer 606is added over the entire surface, as described in U.S. Pat. No.5,643,826; U.S. Pat. No. 5,643,826 is incorporated herein in itsentirety by reference. Ni is used as catalytic material to hastencrystallization of the Si or the S_(1-x)Ge_(x) film. Elements other thanNi, such as Co, Fe, Cu, Pd, Pt, Au or In may be used for this purpose.Crystallization of the Si and Si_(1-x)Ge_(x) films is achieved byfurnace anneal, shown in FIG. 6D, for 8 hours at 600° C. This results ina poly-Si_(1-x)Ge_(x) region 607 and a poly-Si region 608. Thermaltreatment could be carried out using other methods such as laserannealing or lamp annealing.

In FIG. 6E, poly-Si_(1-x)Ge_(x) region 607 is formed into active layer609. Poly-Si region 608 is formed into active layer 610. Active layer609 is for an active layer of TFTs for constituting a later drivercircuit and signal processing circuit. Active layer 610 is for an activelayer of TFTs for constituting a later pixel matrix circuit.

A source region, a drain region, and a lightly doped drain (LDD) regionare formed by a process described in U.S. Pat. No. 5,648,277; U.S. Pat.No. 5,648,277 is incorporated in its entirety by reference. This processwill now be summarized. First, an island pattern, later to be formedinto a gate electrode, is formed by using an Al film containing Sc 2 wt%. Next, anodic oxidation is performed for the island pattern to form aporous anodic oxide film on the side walls of the island pattern. Thenthe solution is changed to further carry out anodic oxidation to form acompact anodic oxide film around the island pattern. After forming theporous anodic oxide film and the compact anodic oxide film in thismanner, a gate dielectric film is etched using a dry etch method. Aftercompleting the etching of the gate dielectric film, the porous anodicoxide film is removed away, thus obtaining the state shown in FIG. 7A.

In FIG. 7A, 711, 712, and 713 are gate insulating films formed bysilicon oxide films, 714, 715 and 716 are gate electrodes formed by Alfilms including Sc, and 717, 718 and 719 are compact anodic oxide filmsfor protecting the gate electrodes. In FIG. 7B, the area to be formedinto a P-channel TFT is covered by a mask 720. The rest of the area hasn-type ions implanted to as to provide n-type conductivity. Twodifferent acceleration voltages are used, as described in U.S. Pat. No.5,648,277, to provide a more uniform distribution of implanted ionconcentration with depth.

In FIG. 7B, the process results in a drain region 721, a source region722, a LDD region 723, and a channel region 724 of an n-channel TFT forconstituting a driver circuit. Also formed are a drain region 726, asource region 725, a LDD region 727, and a channel region 728 of anN-channel TFT for constituting a pixel matrix circuit.

In FIG. 7C, the resist mask 720 is removed and a resist mask 729 isadded to cover the n-type regions. Then impurity ions are implanted toprovide p-type conductivity using two acceleration voltages as describedin U.S. Pat. No. 5,648,277, to provide a more uniform distribution ofimplanted ion concentration with depth. This forms a source region 730,a drain region 731, a LDD region 732 and a channel region 733 of aP-channel TFT for constituting a driver circuit. The impurity ions areactivated through an annealing procedure.

A first interlayer insulating film 734 is formed and contact holes areopened therein to form source electrodes 735, 736, 737 and drainelectrodes 738, 739. The insulating layer 734 may be made of a materialselected from silicon oxide, silicon nitride, silicon oxy-nitride andresin film. The TFTs for the driver circuit are now complete. The TFTsfor the pixel matrix must now be completed. After forming the sourceelectrode and the drain electrode, a second interlayer insulating film740 is formed, then a black mask 741 comprising a Ti film is formedthereon. If one partly removes the second interlayer insulating film ata position over drain electrode 739 prior to forming black mask 741, itis possible to form an auxiliary capacitance from the black mask, thesecond interlayer insulating film, and the drain electrode. Next a thirdinsulating layer film 742 is formed over the black mask 741 and acontact hole is formed therein, and a pixel electrode 743 comprising atransparent conductive film, such as indium tin oxide, is formedthereon.

The active matrix substrate with TFTs, as shown in FIG. 7D, includingintegrally formed pixel and driver circuits which may be adjacent oneanother is thereby disclosed. It will be understood by those skilled inthe art that the CMOS circuit of FIG. 7D could be replaced by othercircuits, such as signal processing circuits, which may be formed on thepoly silicon-germanium region. The poly silicon-germanium regionpossesses high field effect mobility, and hence is suited to high speedoperation. Although the poly Si regions have inferior operating speedcharacteristics compared to the poly silicon-germanium regions, the polySi regions have the better low OFF current characteristics when appliedin the pixel matrix TFTs.

The structures which can be made by this manufacturing method are notlimited to TFT structures but can be applied to any known structures,including bottom-gate TFTs.

Laser Light Sources

RGB solid state laser light sources, e.g. based on GaInAs or GaInAsNmaterials, may be suitable light sources for a holographic displaybecause of their compactness and their high degree of lightdirectionality. Such sources include light emitting diodes as well asthe RGB vertical cavity surface emitting lasers (VCSEL) manufactured byNovalux® Inc., CA, USA. Such laser sources may be supplied as singlelasers or as arrays of lasers, although each source can be used togenerate multiple beams through the use of diffractive optical elements.The beams may be passed down multimode optical fibres as this may reducethe coherence level if the coherence is too high for use in compactholographic displays without leading to unwanted artifacts such as laserspeckle patterns. Arrays of laser sources may be one dimensional or twodimensional.

Substrate

It should be emphasized that the term “substrate” refers to a slab ofmaterial on which the display is manufactured. This would typically bean insulating substrate such as a glass sheet substrate, or a sapphiresubstrate, or a semiconductor substrate such as Si or GaAs, but othersubstrates such as polymer sheets or metal sheets may be possible.Substrates such as glass sheets or semiconductor substrates such as Sior GaAs, are commonly used in device manufacture because they simplifythe processing steps and the transfer between different pieces ofapparatus which perform different process steps, such as materialdeposition, annealing, and material etching. The term “substrate” doesnot refer to a single circuit board, such as is disclosed by Shimobabaet al. Optics Express 13, 4196 (2005): a single circuit board does notpermit the range of manufacturing processes which can be performed on asingle substrate such as a glass sheet substrate.

Estimation of Transistor Count

This section contains an estimation of the number of transistorsrequired in a display, for holographic calculation to be implemented bycircuitry disposed between the pixels of the display.

For implementation using a FPGA, the hologram calculation consists ofthe following steps, where the percentage indicated is the percentage oflogic resources on the FPGA which are used for the given step.

-   -   Lens function: adding random phase and generation of the sub        hologram depending on the z-value (4.5%)    -   CORDIC calculation: transforming the complex values from phase        and magnitude to real and imaginary values, and performing        modulation of the intensity (62.5%)    -   Adding the sub holograms to form the hologram (15.5%)    -   Coding the hologram: the CORDIC algorithm is also used to        convert the values to phase and magnitude and back to real and        imaginary values, and for clipping and normalisation of the data        (17.5%)

Because the transistor counts for memory bits do not depend on thepipeline frequency the percentage numbers given above could be differentwhen computation in the pixel matrix is performed. The computationaleffort for adding and coding will rise with the number of hologrampixels.

The lens function (LF) may have some small LUTs to define thesub-hologram size and the starting constants for the lens functiondepending on the z-value. So the lens function has a relatively highfixed transistor count for the LUTs and a variable transistor countdepending on the number of CORDIC units driven in parallel from the lensfunction every clock cycle. Generally, the size of the computing units(clusters) should be optimised, because the greater their size thesmaller the saving in the data transfer rate will be. On the other handlarger clusters make easier the realisation of the calculations. Theexample of FIG. 23 shows only a simplified cluster design, because onecluster can consist of one million transistors or even more.

Now we estimate the number of transistors required in a display, forholographic calculation to be implemented by circuitry disposed betweenthe pixels of the display. Because the CORDIC algorithm needs more than75% of the resources in the FPGA implementation, the estimation isconcentrated on the transistors to perform the CORDIC calculations. Thereference [CORDIC-Algorithmen, Architekturen and monolithischeRealisierungen mit Anwendungen in der Bildverarbeitung, Dirk Timmermann,1990], incorporated here by reference, from page 100 to page 101 gives alittle help for estimating the CORDIC transistor count. For the FPGAsolution an adapted CORDIC unit was developed that uses differentreductions and so the estimated transistor count for one pipelinedCORDIC unit is about 52,000 transistors.

The spreadsheet in FIGS. 21 and 22 shows the estimation for the plannedhologram computation with 16,000×12,000 hologram pixels starting from a2,000×1,500 pixel real space image. For every pixel in the sub-hologramsone CORDIC operation is needed i.e. 250*10^9 operations per second intotal. With 25 MHz pipeline frequency 9800 CORDIC units in parallel areneeded. The cluster design affects the transistor count and designefficiency because larger clusters mean more expense for thedistribution of the hologram data. But if the cluster is too small,computation within the cluster is not efficient, because some units willdo nothing most of the time and so the transistor count is increased.

If a cluster consists of 1 Lens function unit and 1 CORDIC unit, 9800Clusters and 660 million transistors for sub-hologram computation areneeded. If the cluster consists of 1 Lens function unit and 8 CORDICunits, the display consists of 1200 Clusters and 530 million transistorsfor sub-hologram computation are needed. So the cluster-size may bevaried over a large range and for the sample design a cluster with 4CORDIC units and 1 lens function is chosen. This results in 2500Clusters and 550 million transistors for sub-hologram computation as anestimation.

To find out the optimal cluster size the detailed design must be carriedout. The numbers in the spreadsheet (FIGS. 21 and 22) are only roughestimations but they show the main dependence forms of the parameters.

CORDIC (digit-by-digit method, Volder's algorithm) (for COordinateRotation DIgital Computer) is a simple and efficient algorithm tocalculate hyperbolic and trigonometric functions. Because here CORDIC isused to convert complex numbers from phase and magnitude values to realand imaginary values and vice versa, other algorithms may be used.CORDIC is commonly used if no hardware multiplier (for example, simplemicrocontrollers and FPGAs) is available as it only requires smalllookup tables, bitshifts and additions. Additionally, when implementedin soft or dedicated hardware the CORDIC algorithm is suitable forpipelining. The modern CORDIC algorithm was first described in 1959 byJack E. Volder, although it is similar to techniques published by HenryBriggs as early as 1624. Originally, CORDIC was implemented in binary.In the 1970s, decimal CORDIC became widely used in pocket calculators,most of which operate not in binary but in binary-coded-decimal (BCD).CORDIC is particularly well-suited for handheld calculators, anapplication for which cost (and therefore gate count on the chip) ismuch more important than is speed. CORDIC is generally faster than otherapproaches when a hardware multiplier is unavailable (e.g. in amicrocontroller), or when the number of gates required to implement oneneeds to be minimized (e.g. in an FPGA).

CORDIC is part of the class of “shift-and-add” algorithms, as are thelogarithm and exponential algorithms derived from Henry Briggs' work.Another shift-and-add algorithm which can be used for computing manyelementary functions is the BKM algorithm, which is a generalization ofthe logarithm and exponential algorithms to the complex plane. Forinstance, BKM can be used to compute the sine and cosine of a real anglex (in radians) by computing the exponential of 0+ix, which iscosx+isinx. The BKM algorithm, first published in 1994 by J. C. Bajard,S. Kla, and J. M. Muller, IEEE Transactions on Computers, 43(8):955-963, August 1994, is slightly more complex than CORDIC, but has theadvantage that it does not need a scaling factor. BKM algorithms may beused instead of CORDIC algorithms in the present implementation.

Computation Methods

Today, central processing units (CPUs) and Digital Signal Processor(DSP)-units mainly use digital synchronous logic for computation. TheFPGA hologram computation may also use this approach. Because of the lowtransistor count per hologram pixel other methods may be preferreddepending on the computation step. The following list shows the mainattributes for some other computation methods:

Digital Synchronous Logic (Clocked Logic)

-   -   high transistor count    -   short computation time    -   easy timing calculation    -   good design tool support        Digital Asynchronous Logic (Unclocked Logic)    -   good power efficiency    -   high transistor count    -   short computation time    -   poor design tool support    -   difficult timing calculation        PWM (Pulse Width Modulation)    -   low transistor count    -   long computation time        Analogue    -   mainly developed from 1950 to 1960    -   except for simple high frequency uses, analogue computing is        uncommon today    -   very low transistor count    -   short computation time    -   limited precision    -   high production parameter drift dependence        Mixed Technologies

The requirements of the computation steps are different. Because of thelimited capacity of e.g. poly-Si transistors the computation methodshould be chosen depending on the requirements. The optimal method willdepend on the precise implementation. Some examples follow.

To lower the number of transistors, computation steps with lowrequirements such as the lens function and coding can use PWM. Analogueshift registers may be used for data distribution because real spacedata and hologram data uses only about 8-bit precision. A speciallydesigned asynchronous CORDIC unit can be used to reduce powerdissipation. Using more than one method per step may further reduce thenumber of transistors but may raise the design costs.

Display Types

The display is preferably an active matrix structure using transistorsor other switching elements (e.g. electrical, optical) on the displaysurface. The transistor material should have an adequate structuralwidth and switching frequency to implement the additional transistorsfor the computation. Mono-crystal silicon and poly-Si variants such aslow temperature poly-Si (LTPS), CGS, single grain Si or poly-SiGe can beused. The switching frequency of amorphous silicon is generally too lowfor high performance hologram calculation. In principle, organicsemiconductors or carbon nanotubes may also be used as switching elementmaterials. Conventional large displays require large areas for row andcolumn lines. This area can be saved using the present approach.

Because the area savings are higher on larger displays, the followingdisplay types are preferred:

-   -   liquid crystal display (LCD) on LTPS    -   Organic light emitting diodes (OLED) (including light emitting        polymers (LEP)) on LTPS

Mono-crystalline silicon is used only for small displays with feweradvantages compared to the new method. Examples of the use ofmono-crystalline Si are:

-   -   LCOS    -   Digital Light Processing (DLP) technology

A list of possible display technologies which may be used for animplementation is:

Liquid Crystal Display (LCD)-Types

-   -   LCOS liquid crystal on silicon    -   NLC nematic liquid crystal    -   TN twisted nematic    -   VAN vertical aligned nematic    -   FLC Ferroelectric liquid crystal        FED (Field Emission Displays)    -   SED Surface-Conduction Electron-Emitter Display    -   carbon nanotube emitters (based on silicon substrates or indium        tin oxide (ITO) coated glass substrates, but these can be used        as light sources only, because non coherent light is emitted)        Electro Mechanical Systems    -   Mirror arrays/Digital Light Processing (DLP) technology    -   MEMS mirrors (Micro Electro Mechanical Systems), also referred        to as MOEMS    -   (micro-opto-electromechanical system)        A List of Hologram Calculation Methods is:    -   look-up tables (LUT)    -   Analytical computation    -   the method described in patent publication number WO        2006/066919, incorporated herein by reference.    -   Ray-tracing method        Transformation Types:    -   2D Transformation    -   1D Transformation in the horizontal plane    -   1D Transformation in the vertical plane        Encoding Types:    -   Burckhardt encoding    -   Phase only encoding    -   Two phase encoding    -   BIAS encoding    -   MDE (minimum distance encoding)-Encoding using more than 3 SLM        pixels per hologram pixel        Hardware

An external hologram calculation unit may consist of a couple of highend FPGAs or an application specific integrated circuit (ASIC) or a fullcustom integrated circuit (IC) with about 52 million transistors and a500 MHz pipeline frequency. To transfer the data to the display about230 low voltage differential signalling (LVDS) pairs each transmittingat 1 Gbits per second can be used. To receive the data, chip on glass(COG) row- and column-line drivers are also needed. If the computationis integrated on the display substrate only high switching frequencyparts like the Digital Visual Interface (DVI) receiver must beimplemented in additional hardware. Only the original data with 50-timeslower data rate must be transferred (see FIG. 1). Very cheap displayelectronics with only a few connections to the display can be used. Thiselectronics is nearly the same as in today's low-resolution 2D TFTDisplays.

Notes

Features of the above three outline manufacturing methods may becombined without departing from the scope of the invention.

In the Figures herein, the relative dimensions shown are not necessarilyto scale.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scope ofthis invention, and it should be understood that this invention is notto be unduly limited to the illustrative examples set forth herein.

There are multiple concepts (described as ‘Concepts A-T’) in thisdisclosure. Appendix III contains text which may be helpful in definingthese concepts. As would be clear to one skilled in the art, disclosureswith respect to one concept may be of assistance in elucidating aspectsof other concepts. Some of these concepts may form part of theinvention, as will be clear from elsewhere in this document.

APPENDIX I Technical Primer

The following section is meant as a primer to several key techniquesused in some of the systems that implement the present invention.

In conventional holography, the observer can see a holographicreconstruction of an object (which could be a changing scene); hisdistance from the hologram is not however relevant. The reconstructionis, in one typical optical arrangement, at or near the image plane ofthe light source illuminating the hologram and hence is at or near theFourier plane of the hologram. Therefore, the reconstruction has thesame far-field light distribution of the real world object that isreconstructed.

One early system (described in WO 2004/044659 and US 2006/0055994, whichare incorporated herein in their entirety by reference) defines a verydifferent arrangement in which the reconstructed object is not at ornear the Fourier plane of the hologram at all. Instead, a virtualobserver window zone is at the Fourier plane of the hologram; theobserver positions his eyes at this location and only then can a correctreconstruction be seen. The hologram is encoded on a LCD (or other kindof spatial light modulator) and illuminated in an optical set-up so thatthe virtual observer window becomes the Fourier transform of thehologram (hence it is a Fourier transform that is imaged directly ontothe eyes); the reconstructed object formed in the frustum spanned by theobserver window and the SLM is then a propagation better described bythe Fresnel transform of the hologram since it is not in the focus planeof the lens. It is instead defined by a near-field light distribution(modelled using spherical wavefronts, as opposed to the planarwavefronts of a far field distribution). This reconstruction can appearanywhere between the virtual observer window (which is, as noted above,in the Fourier plane of the hologram) and the SLM or even behind the SLMas a virtual object.

There are several consequences to this approach. First, the fundamentallimitation facing designers of holographic video systems is the pixelpitch of the SLM (or other kind of light modulator). The goal is toenable large holographic reconstructions using SLMs with pixel pitchesthat are commercially available at reasonable cost. But in the past thishas been impossible for the following reason. The periodicity intervalbetween adjacent diffraction orders in the Fourier plane is given byλD/p, where λ is the wavelength of the illuminating light, D is thedistance from the hologram to the Fourier plane and p is the pixel pitchof the SLM. But in conventional holographic displays, the reconstructedobject is in or near the Fourier plane. Hence, a reconstructed objecthas to be kept smaller than the periodicity interval; if it were larger,then its edges would blur into a reconstruction from an adjacentdiffraction order. This leads to very small reconstructedobjects—typically just a few cm across, even with costly, specialisedsmall pitch displays. But with the present approach, the virtualobserver window (which is, as noted above, positioned to be in theFourier plane of the hologram) need only be as large as the eye pupil.As a consequence, even SLMs with a moderate pitch size can be used. Andbecause the reconstructed object can entirely fill the frustum betweenthe virtual observer window and the hologram, it can be very largeindeed, i.e. much larger than the periodicity interval. Further, wherean OASLM is used, then there is no pixelation, and hence no periodicity,so that the constraint of keeping the virtual observer window smallerthan a periodicity interval no longer applies.

There is another advantage as well, deployed in one variant. Whencomputing a hologram, one starts with one's knowledge of thereconstructed object—e.g. you might have a 3D image file of a racingcar. That file will describe how the object should be seen from a numberof different viewing positions. In conventional holography, the hologramneeded to generate a reconstruction of the racing car is deriveddirectly from the 3D image file in a computationally intensive process.But the virtual observer window approach enables a different and morecomputationally efficient technique. Starting with one plane of thereconstructed object, we can compute the virtual observer window as thisis the Fresnel transform of the object. We then perform this for allobject planes, summing the results to produce a cumulative Fresneltransform; this defines the wave field across the virtual observerwindow. We then compute the hologram as the Fourier transform of thisvirtual observer window. As the virtual observer window contains all theinformation of the object, only the single-plane virtual observer windowhas to be Fourier transformed to the hologram and not the multi-planeobject. This is particularly advantageous if there is not a singletransformation step from the virtual observer window to the hologram butan iterative transformation like the Iterative Fourier TransformationAlgorithm. If iteration is needed, each iteration step comprises only asingle Fourier transformation of the virtual observer window instead ofone for each object plane, resulting in significantly reducedcomputation effort.

Another interesting consequence of the virtual observer window approachis that all the information needed to reconstruct a given object pointis contained within a relatively small section of the hologram; thiscontrasts with conventional holograms in which information toreconstruct a given object point is distributed across the entirehologram. Because we need encode information into a substantiallysmaller section of the hologram, that means that the amount ofinformation we need to process and encode is far lower than for aconventional hologram. That in turn means that conventionalcomputational devices (e.g. a conventional DSP with cost and performancesuitable for a mass market device) can be used even for real time videoholography.

There are some less than desirable consequences however. First, theviewing distance from the hologram is important—the hologram is encodedand illuminated in such a way that only when the eyes are positioned ator near the Fourier plane of the hologram is the correct reconstructionseen; whereas in normal holograms, the viewing distance is notimportant. There are however various techniques for reducing this Zsensitivity or designing around it.

Also, because the hologram is encoded and illuminated in such a way thatcorrect holographic reconstructions can only be seen from a precise andsmall viewing position (i.e. in particular in lateral positioning butalso in Z distance), eye tracking may be needed. As with Z sensitivity,various techniques for reducing the X,Y sensitivity or designing aroundit exist. For example, as pixel pitch decreases (as it will with SLMmanufacturing advances), the virtual observer window size will increase.Furthermore, more efficient encoding techniques (like Kinoform encoding)facilitate the use of a larger part of the periodicity interval asvirtual observer window and hence the increase of the virtual observerwindow.

The above description has assumed that we are dealing with Fourierholograms. The virtual observer window is in the Fourier plane of thehologram, i.e. in the image plane of the light source. As an advantage,the undiffracted light is focused in the so-called DC-spot. Thetechnique can also be used for Fresnel holograms where the virtualobserver window is not in the image plane of the light source. However,care should be taken that the undiffracted light is not visible as adisturbing background. Another point to note is that the term“transform” should be construed to include any mathematical orcomputational technique that is equivalent to or approximates to atransform that describes the propagation of light. Transforms are merelyapproximations to physical processes more accurately defined byMaxwellian wave propagation equations; Fresnel and Fourier transformsare second order approximations, but have the advantages that (a)because they are algebraic as opposed to differential, they can behandled in a computationally efficient manner and (ii) can be accuratelyimplemented in optical systems.

Further details are given in US patent application 2006-0138711, US2006-0139710 and US 2006-0250671, the contents of which are incorporatedby reference.

APPENDIX II Glossary of Terms Used in the Description

Computer Generated Hologram

A computer generated video hologram CGH is a hologram that is calculatedfrom a scene. The CGH may comprise complex-valued numbers representingthe amplitude and phase of light waves that are needed to reconstructthe scene. The CGH may be calculated e.g. by coherent ray tracing, bysimulating the interference between the scene and a reference wave, orby Fourier or Fresnel transform.

Encoding

Encoding is the procedure in which a spatial light modulator (e.g. itsconstituent cells, or contiguous regions for a continuous SLM like anOASLM) are supplied with control values of the video hologram. Ingeneral, a hologram comprises of complex-valued numbers representingamplitude and phase.

Encoded Area

The encoded area is typically a spatially limited area of the videohologram where the hologram information of a single scene point isencoded. The spatial limitation may either be realized by an abrupttruncation or by a smooth transition achieved by Fourier transform of anvirtual observer window to the video hologram.

Fourier Transform

The Fourier transform is used to calculate the propagation of light inthe far field of the spatial light modulator. The wave front isdescribed by plane waves.

Fourier Plane

The Fourier plane contains the Fourier transform of the lightdistribution at the spatial light modulator. Without any focusing lensthe Fourier plane is at infinity. The Fourier plane is equal to theplane containing the image of the light source if a focusing lens is inthe light path close to the spatial light modulator.

Fresnel Transform

The Fresnel transform is used to calculate the propagation of light inthe near field of the spatial light modulator. The wave front isdescribed by spherical waves. The phase factor of the light wavecomprises a term that depends quadratically on the lateral coordinate.

Frustum

A virtual frustum is constructed between a virtual observer window andthe SLM and is extended behind the SLM. The scene is reconstructedinside this frustum. The size of the reconstructed scene is limited bythis frustum and not by the periodicity interval of the SLM.

Light System

The light system may include either of a coherent light source like alaser or a partially coherent light source like a LED. The temporal andspatial coherence of the partially coherent light source has to besufficient to facilitate a good scene reconstruction, i.e. the spectralline width and the lateral extension of the emitting surface have to besufficiently small.

Virtual Observer Window (VOW)

The virtual observer window is a virtual window in the observer planethrough which the reconstructed 3D object can be seen. The VOW is theFourier transform of the hologram and is positioned within oneperiodicity interval in order to avoid multiple reconstructions of theobject being visible. The size of the VOW has to be at least the size ofan eye pupil. The VOW may be much smaller than the lateral range ofobserver movement if at least one VOW is positioned at the observer'seyes with an observer tracking system. This facilitates the use of a SLMwith moderate resolution and hence small periodicity interval. The VOWcan be imagined as a keyhole through which the reconstructed 3D objectcan be seen, either one VOW for each eye or one VOW for both eyestogether.

Periodicity Interval

The CGH is sampled if it is displayed on a SLM composed of individuallyaddressable cells. This sampling leads to a periodic repetition of thediffraction pattern. The periodicity interval is λD/p, where λ is thewavelength, D the distance from the hologram to the Fourier plane, and pthe pitch of the SLM cells. OASLMs however have no sampling and hencethere is no periodic repetition of the diffraction pattern; therepetitions are in effect suppressed.

Reconstruction

The illuminated spatial light modulator encoded with the hologramreconstructs the original light distribution. This light distributionwas used to calculate the hologram. Ideally, the observer would not beable to distinguish the reconstructed light distribution from theoriginal light distribution. In most holographic displays the lightdistribution of the scene is reconstructed. In our display, rather thelight distribution in the virtual observer window is reconstructed.

Scene

The scene that is to be reconstructed is a real or computer generatedthree-dimensional light distribution. As a special case, it may also bea two-dimensional light distribution. A scene can constitute differentfixed or moving objects arranged in a space.

Spatial Light Modulator (SLM)

A SLM is used to modulate the wave front of the incoming light. An idealSLM would be capable of representing arbitrary complex-valued numbers,i.e. of separately controlling the amplitude and the phase of a lightwave. However, a typical conventional SLM controls only one property,either amplitude or phase, with the undesirable side effect of alsoaffecting the other property.

APPENDIX III Concepts

There are multiple concepts (described as ‘Concepts A-T’) in thisdisclosure. The following may be helpful in defining these concepts.

A. Hologram Display with Calculation on the Same Substrate as the Pixels

Holographic display in which at least some of the calculations performedto determine the encoding of a spatial light modulator are performedusing circuitry which is on the same substrate as the pixels of thespatial light modulator.

-   -   at least some of the calculations performed to determine the        encoding of the spatial light modulator are performed using        circuitry which is between the pixels of the spatial light        modulator.    -   the calculations are performed in discrete areas of the display,        to encode the pixels of the corresponding discrete areas, on a        discrete area by discrete area basis.    -   the circuitry includes thin film transistors.    -   the active regions of at least some of the circuitry consists of        polycrystalline Si.    -   the active regions of at least some of the circuitry consists of        continuous grain Si.    -   the active regions of at least some of the circuitry consists of        polycrystalline SiGe.    -   the active regions of at least some of the circuitry consists of        monocrystalline Si.    -   the active regions of at least some of the circuitry consists of        single grain Si.    -   the active regions of at least some of the circuitry consists of        organic semiconductors.    -   the substrate is monocrystalline Si.    -   the substrate is glass.    -   only real space image data is transmitted to the display.    -   the video frame rate is at least about 25 Hz.    -   the image data consists of intensity and depth map data.    -   the holographic calculation is performed in real time or in        quasi real time.    -   the holographic calculation is performed using a look-up table        approach.    -   sub-holograms are used for computation.    -   data for adding the sub holograms is exchanged over the distance        of a sub-hologram dimension.    -   the holographic computation is spread homogeneously over the        whole display surface.    -   the holographic computation is split into small identical parts        called clusters tiled over the display surface.    -   data for adding the sub holograms is exchanged over the distance        of a cluster dimension.    -   the holographic display can be built up through tiling identical        clusters together.    -   the holographic display is a high resolution display.    -   the holographic display is a very high resolution display.    -   a virtual observer window is an eye pupil diameter or more        across.    -   the virtual observer window is one cm or more across.    -   one depth map and intensity map pair is constructed for each eye        i.e. for each virtual observer window.    -   monochrome images are displayed.    -   colour images are displayed.    -   the colour images displayed are in RGB format.    -   in order to calculate the value of a pixel of the hologram, only        values of a sub-section of the original image are considered.    -   the light used for the reconstruction is not fully coherent        across the entire display, but rather coherence exists within        sub-sections of the display.    -   fewer wires are sufficient for the transfer of original image        data than for the transmission of hologram data.    -   reducing the data transmission frequency has the benefit of        reducing the power dissipation in the row and column drivers.    -   the large proportion of the pixel area which was required in        prior art solutions for column and row wires can be used for        other purposes.    -   the area of the transparent electrode can be increased and thus        the transmittance of the display can be improved.    -   the display panel can be controlled using conventional display        technologies.    -   the display is fabricated using liquid crystal on silicon        technology.    -   the display is fabricated using MEMS technology.    -   the display is fabricated using field emission display        technology.    -   the holographic transformation is a one dimensional        transformation.    -   the holographic transformation is a two dimensional        transformation.    -   an additional logic for local forwarding of calculated data        exists, and the additional logic can also be co-used for        forwarding the original image to the clusters, so that at least        some global row and column wires may be eliminated.    -   redundant circuitry, such as TFTs, may be manufactured in the        space of the pixel matrix so that such circuitry can be used to        replace some of the circuitry used at device start up, if some        of the circuitry used at device start up is found to have        failed.    -   Method of using the holographic display.        B. Hologram Display with Calculation on the Same Substrate, with        Efficient Calculation of the Encoding for the Spatial Light        Modulator

Holographic display in which at least some of the calculations performedto determine the encoding of a spatial light modulator are performedusing circuitry which is on the same substrate as the pixels of thespatial light modulator, and where the calculations do not involve thecalculation of a Fourier transform or of a Fresnel transform per se.

-   -   at least some of the calculations performed to determine the        encoding of the spatial light modulator are performed using        circuitry which is between the pixels of the spatial light        modulator.    -   the calculations are performed in discrete areas of the display,        to encode the pixels of the corresponding discrete areas, on a        discrete area by discrete area basis.    -   the circuitry includes thin film transistors.    -   the active regions of at least some of the circuitry consists of        polycrystalline Si.    -   the active regions of at least some of the circuitry consists of        continuous grain Si.    -   the active regions of at least some of the circuitry consists of        polycrystalline SiGe.    -   the active regions of at least some of the circuitry consists of        monocrystalline Si.    -   the active regions of at least some of the circuitry consists of        single grain Si.    -   the active regions of at least some of the circuitry consists of        organic semiconductors.    -   the substrate is monocrystalline Si.    -   the substrate is glass.    -   only real space image data is transmitted to the display.    -   the video frame rate is at least about 25 Hz.    -   the image data consists of intensity and depth map data.    -   the holographic calculation is performed in real time or in        quasi real time.    -   the holographic calculation is performed using a look-up table        approach.    -   sub-holograms are used for computation.    -   the holographic computation is spread homogeneously over the        whole display surface.    -   the holographic computation is split into small identical parts        called clusters tiled over the display surface.    -   the holographic display is a high resolution display.    -   a virtual observer window is an eye pupil diameter or more        across.    -   monochrome images are displayed.    -   colour images are displayed.    -   in order to calculate the value of a pixel of the hologram, only        values of a sub-section of the original image are considered.    -   the light used for the reconstruction is not fully coherent        across the entire display, but rather coherence exists within        sub-sections of the display.    -   fewer wires are sufficient for the transfer of original image        data than for the transmission of hologram data.    -   reducing the data transmission frequency has the benefit of        reducing the power dissipation in the row and column drivers.    -   the large proportion of the pixel area which was required in        prior art solutions for column and row wires can be used for        other purposes.    -   the area of the transparent electrode can be increased and thus        the transmittance of the display can be improved.    -   the display panel can be controlled using conventional display        technologies.    -   the display is fabricated using liquid crystal on silicon        technology.    -   the display is fabricated using MEMS technology.    -   the display is fabricated using field emission display        technology.    -   the holographic transformation is a one dimensional        transformation.    -   the holographic transformation is a two dimensional        transformation.    -   an additional logic for local forwarding of calculated data        exists, and the additional logic can also be co-used for        forwarding the original image to the clusters, so that at least        some global row and column wires may be eliminated.    -   redundant circuitry, such as TFTs, may be manufactured in the        space of the pixel matrix so that such circuitry can be used to        replace some of the circuitry used at device start up, if some        of the circuitry used at device start up is found to have        failed.    -   the wavefront which would be emitted by the object is        reconstructed in one or multiple virtual observer windows (VOW)        and where the reconstruction of each single object point (OP) of        a three-dimensional scene (3D S) only requires a sub-hologram        (SH) as a subset of the entire hologram (HΣSLM) to be encoded on        the SLM.    -   after a discretization of the scene (3D S) to multiple        object-points (OP), for each visible object-point (OP) of the        3D-scene, the complex values of the lens sub-hologram (SH_(L))        are encoded on the SLM, where the complex values of the lens        sub-hologram are determined using the formula        z_(L)=exp{−i*[(π/λf)*(x²+y²)]} with λ as the        reference-wave-length, f as focal length, and x and y being        orthogonal coordinates in the plane of the sub-hologram.    -   the sub-hologram (SH_(P)) of the prism is determined within the        hologram-plane (HE) in order to move the virtual observer window        away from the optic axis.    -   the sub-holograms of the lens and of the prisms are convolved,        which can be represented symbolically as SH=SH_(L)*SH_(P).    -   each sub-hologram (SH) is modulated with a uniformly distributed        phase shift, where the phase shift is different from        sub-hologram to sub-hologram.    -   the sub-holograms are added so as to form the entire hologram.    -   the representation of computer-generated holograms for        reconstructions which vary in real-time or in quasi real-time.    -   look-up tables are used in the holographic calculation.    -   the object points can be generated at any position within the        reconstruction frustum.    -   Method of using the holographic display.        C. Hologram Display with Decompression Calculation on the Same        Substrate

Holographic display in which the hologram encoding data is calculatedoutside the space occupied by the pixel matrix, the hologram encodingdata is then compressed using known data compression techniques, and isthen transmitted to circuitry on the display substrate, the circuitrythen performing the function of decompressing the data which has beenreceived.

-   -   at least some of the calculations performed to determine the        encoding of a spatial light modulator are performed using        circuitry which is on the same substrate as the pixels of the        spatial light modulator.    -   the circuitry includes thin film transistors.    -   the active regions of at least some of the circuitry consists of        polycrystalline Si.    -   the active regions of at least some of the circuitry consists of        continuous grain Si.    -   the active regions of at least some of the circuitry consists of        polycrystalline SiGe.    -   the active regions of at least some of the circuitry consists of        monocrystalline Si.    -   the active regions of at least some of the circuitry consists of        single grain Si.    -   the active regions of at least some of the circuitry consists of        organic semiconductors.    -   the substrate is monocrystalline Si.    -   the substrate is glass.    -   the video frame rate is at least about 25 Hz.    -   the image data consists of intensity and depth map data.    -   the holographic calculation is performed in real time or in        quasi real time.    -   the holographic calculation is performed using a look-up table        approach.    -   sub-holograms are used for computation.    -   the holographic display is a high resolution display.    -   a virtual observer window is an eye pupil diameter or more        across.    -   monochrome images are displayed.    -   colour images are displayed.    -   in order to calculate the value of a pixel of the hologram, only        values of a sub-section of the original image are considered.    -   the light used for the reconstruction is not fully coherent        across the entire display, but rather coherence exists within        sub-sections of the display.    -   reducing the data transmission frequency has the benefit of        reducing the power dissipation in the row and column drivers.    -   the large proportion of the pixel area which was required in        prior art solutions for column and row wires can be used for        other purposes.    -   the area of the transparent electrode can be increased and thus        the transmittance of the display can be improved.    -   the display panel can be controlled using conventional display        technologies.    -   the display is fabricated using liquid crystal on silicon        technology.    -   the display is fabricated using MEMS technology.    -   the display is fabricated using field emission display        technology.    -   the holographic transformation is a one dimensional        transformation.    -   the holographic transformation is a two dimensional        transformation.    -   redundant circuitry, such as TFTs, may be manufactured in the        space of the pixel matrix so that such circuitry can be used to        replace some of the circuitry used at device start up, if some        of the circuitry used at device start up is found to have        failed.    -   the wavefront which would be emitted by the object is        reconstructed in one or multiple virtual observer windows (VOW)        and where the reconstruction of each single object point (OP) of        a three-dimensional scene (3D S) only requires a sub-hologram        (SH) as a subset of the entire hologram (HΣSLM) to be encoded on        the SLM.    -   after a discretization of the scene (3D S) to multiple        object-points (OP), for each visible object-point (OP) of the        3D-scene, the complex values of the lens sub-hologram (SH_(L))        are encoded on the SLM, where the complex values of the lens        sub-hologram are determined using the formula        z_(L)=exp{−i*[(π/λf)*(x²+y²)]} with λ as the        reference-wave-length, f as focal length, and x and y being        orthogonal coordinates in the plane of the sub-hologram.    -   the sub-hologram (SH_(P)) of the prism is determined within the        hologram-plane (HE) in order to move the virtual observer window        away from the optic axis.    -   the sub-holograms of the lens and of the prisms are convolved,        which can be represented symbolically as SH=SH_(L)*SH_(P).    -   the space in which the holographic calculations are performed        may or may not be on the same substrate as the display's        substrate.    -   the circuitry where the decompression calculations are performed        is situated between the pixels of the display.    -   the circuitry where the decompression calculations are performed        is situated outside the pixel matrix of the display, but on the        same substrate.    -   clusters perform the decompression calculation.    -   clusters for the decompression calculation receive data via the        display's row and column wires.    -   each cluster for the decompression calculation receives data via        a parallel data bus.    -   each cluster for the decompression calculation receives data via        a serial data connection.    -   Method of using the holographic display.        D. High Resolution Display with Decompression Calculation on the        Same Substrate

A high resolution display on which high resolution image data isdisplayed, where the data is first compressed using known datacompression techniques, and is then transmitted to circuitry on thesubstrate of the display, the circuitry then performing the function ofdecompressing the data which has been received with subsequent displayof the data at the pixels of the display.

-   -   the decompression circuitry is located between the pixels of the        display.    -   the decompression circuitry is located outside the pixel matrix        of the display, but on the same substrate as the display.    -   compressed data is transmitted to the display clusters which are        part of the whole display, the clusters then performing the        function of decompressing the data which has been received and        then displaying the data at pixels of the local cluster.    -   normal display data is displayed.    -   holographic display data is displayed.    -   the space in which the compression calculations are performed        may or may not be on the same substrate as the display's        substrate.    -   the clusters for the decompression calculation receive data via        the display's row and column wires.    -   each cluster for the decompression calculation receives data via        a parallel data bus.    -   each cluster for the decompression calculation receives data via        a serial data connection.    -   is a very high resolution display.    -   decompression is performed by each cluster in 40 ms or less.    -   holographic image calculation is performed after decompression.    -   at least some of the calculations performed to determine the        encoding of a spatial light modulator are performed using        circuitry which is on the same substrate as the pixels of the        spatial light modulator.    -   at least some of the calculations performed to determine the        encoding of a spatial light modulator are performed using        circuitry which is on the same substrate as the pixels of the        spatial light modulator, and where the calculations do not        involve the calculation of a Fourier transform or of a Fresnel        transform per se.    -   at least some of the calculations performed to determine the        encoding of the spatial light modulator are performed using        circuitry which is between the pixels of the spatial light        modulator.    -   the calculations are performed in discrete areas of the display,        to encode the pixels of the corresponding discrete areas, on a        discrete area by discrete area basis.    -   the circuitry includes thin film transistors.    -   the active regions of at least some of the circuitry consists of        polycrystalline Si.    -   the active regions of at least some of the circuitry consists of        continuous grain Si.    -   the active regions of at least some of the circuitry consists of        polycrystalline SiGe.    -   the active regions of at least some of the circuitry consists of        monocrystalline Si.    -   the active regions of at least some of the circuitry consists of        single grain Si.    -   the active regions of at least some of the circuitry consists of        organic semiconductors.    -   the substrate is monocrystalline Si.    -   the substrate is glass.    -   the video frame rate is at least about 25 Hz.    -   only real space image data is transmitted to the display.    -   the image data consists of intensity and depth map data.    -   the holographic calculation is performed in real time or in        quasi real time.    -   the holographic calculation is performed using a look-up table        approach.    -   sub-holograms are used for computation.    -   the display is fabricated using liquid crystal on silicon        technology.    -   the display is fabricated using MEMS technology.    -   the display is fabricated using field emission display        technology.    -   Method of using the high resolution display.        E. Hologram Display with Calculation on the Same Substrate, with        an Extended 3D Rendering Pipeline for the Graphics Sub-Systems        by Incorporating Additional Processing Units for Holographic        Transformation and Encoding

Holographic display in which at least some of the calculations performedto determine the encoding of a spatial light modulator are performedusing circuitry which is on the same substrate as the pixels of thespatial light modulator, such that the 3D rendering pipeline of graphicssub-systems incorporates additional processing units for holographictransformation and encoding.

-   -   the holographic calculations are performed using circuitry which        is in between the pixels of the display.    -   the holographic calculations are performed using circuitry which        is outside the pixel matrix of the display, but on the same        substrate as the pixels of the display.    -   at least some of the calculations performed to determine the        encoding of a spatial light modulator are performed using        circuitry which is on the same substrate as the pixels of the        spatial light modulator, and where the calculations do not        involve the calculation of a Fourier transform or of a Fresnel        transform per se.    -   the calculations are performed in discrete areas of the display,        to encode the pixels of the corresponding discrete areas, on a        discrete area by discrete area basis.    -   the circuitry includes thin film transistors.    -   the video frame rate is at least about 25 Hz.    -   only real space image data is transmitted to the display.    -   the image data consists of intensity and depth map data.    -   the holographic calculation is performed in real time or in        quasi real time.    -   the holographic calculation is performed using a look-up table        approach.    -   sub-holograms are used for computation.    -   the holographic computation is spread homogeneously over the        whole display surface.    -   the holographic computation is split into small identical parts        called clusters tiled over the display surface.    -   the holographic display is a high resolution display.    -   a virtual observer window is an eye pupil diameter or more        across.    -   monochrome images are displayed.    -   colour images are displayed.    -   in order to calculate the value of a pixel of the hologram, only        values of a sub-section of the original image are considered.    -   the light used for the reconstruction is not fully coherent        across the entire display, but rather coherence exists within        sub-sections of the display.    -   the holographic transformation is a one dimensional        transformation.    -   the holographic transformation is a two dimensional        transformation.    -   redundant circuitry, such as TFTs, may be manufactured in the        space of the pixel matrix so that such circuitry can be used to        replace some of the circuitry used at device start up, if some        of the circuitry used at device start up is found to have        failed.    -   the wavefront which would be emitted by the object is        reconstructed in one or multiple virtual observer windows (VOW)        and where the reconstruction of each single object point (OP) of        a three-dimensional scene (3D S) only requires a sub-hologram        (SH) as a subset of the entire hologram (HΣSLM) to be encoded on        the SLM.    -   after a discretization of the scene (3D S) to multiple        object-points (OP), for each visible object-point (OP) of the        3D-scene, the complex values of the lens sub-hologram (SH_(L))        are encoded on the SLM, where the complex values of the lens        sub-hologram are determined using the formula        z_(L)=exp{−i*[(π/λf)*(x²+y²)]} with λ as the        reference-wave-length, f as focal length, and x and y being        orthogonal coordinates in the plane of the sub-hologram.    -   the sub-hologram (SH_(P)) of the prism is determined within the        hologram-plane (HE) in order to move the virtual observer window        away from the optic axis.    -   the sub-holograms of the lens and of the prisms are convolved,        which can be represented symbolically as SH=SH_(L)*SH_(P).    -   each sub-hologram (SH) is modulated with a uniformly distributed        phase shift, where the phase shift is different from        sub-hologram to sub-hologram.    -   the sub-holograms are added so as to form the entire hologram.    -   for the representation of computer-generated holograms for        reconstructions which vary in real-time or in quasi real-time.    -   look-up tables are used in the holographic calculation.    -   the object points can be generated at any position within the        reconstruction frustum.    -   the Z map for the first display wavelength is copied twice for        the second and third display wavelengths.    -   the hologram is calculated for each of the three display        wavelengths in parallel.    -   the colour map RGB contents for two colours are copied to        separate memory sections, so as to ensure independent access to        the three colour components.    -   the lens function and the prism function for each display colour        undergoes a complex multiplication.    -   a random phase is applied for each cluster of the display.    -   the calculated SLM encodings are subjected to subsequent        processing, using additional algorithms in the holographic        display cluster.    -   Method of using the holographic display.        F. Hologram Display with Calculation on the Same Substrate, with        Sequential Holographic Transformation of Points in        Three-Dimensional Space by Way of Extending the 3D Pipeline of        Graphics Cards with a Holographic Calculation Pipeline

Holographic display in which at least some of the calculations performedto determine the encoding of a spatial light modulator are performedusing circuitry which is on the same substrate as the pixels of thespatial light modulator, such that sequential holographic transformationof points in three-dimensional space is performed by way of extendingthe 3D pipeline of graphics cards with a holographic calculationpipeline.

-   -   the holographic calculations are performed using circuitry which        is in between the pixels of the display.    -   the holographic calculations are performed using circuitry which        is outside the pixel matrix, but on the same substrate as the        display.    -   at least some of the calculations performed to determine the        encoding of a spatial light modulator are performed using        circuitry which is on the same substrate as the pixels of the        spatial light modulator, and where the calculations do not        involve the calculation of a Fourier transform or of a Fresnel        transform per se.    -   the calculations are performed in discrete areas of the display,        to encode the pixels of the corresponding discrete areas, on a        discrete area by discrete area basis.    -   the circuitry includes thin film transistors.    -   the video frame rate is at least about 25 Hz.    -   only real space image data is transmitted to the display.    -   the image data consists of intensity and depth map data.    -   the holographic calculation is performed in real time or in        quasi real time.    -   the holographic calculation is performed using a look-up table        approach.    -   sub-holograms are used for computation.    -   the holographic computation is spread homogeneously over the        whole display surface.    -   the holographic computation is split into small identical parts        called clusters tiled over the display surface.    -   the holographic display is a high resolution display.    -   a virtual observer window is an eye pupil diameter or more        across.    -   monochrome images are displayed.    -   colour images are displayed.    -   in order to calculate the value of a pixel of the hologram, only        values of a sub-section of the original image are considered.    -   the light used for the reconstruction is not fully coherent        across the entire display, but rather coherence exists within        sub-sections of the display.    -   the holographic transformation is a one dimensional        transformation.    -   the holographic transformation is a two dimensional        transformation.    -   redundant circuitry, such as TFTs, may be manufactured in the        space of the pixel matrix so that such circuitry can be used to        replace some of the circuitry used at device start up, if some        of the circuitry used at device start up is found to have        failed.    -   the wavefront which would be emitted by the object is        reconstructed in one or multiple virtual observer windows (VOW)        and where the reconstruction of each single object point (OP) of        a three-dimensional scene (3D S) only requires a sub-hologram        (SH) as a subset of the entire hologram (HΣSLM) to be encoded on        the SLM.    -   after a discretization of the scene (3D S) to multiple        object-points (OP), for each visible object-point (OP) of the        3D-scene, the complex values of the lens sub-hologram (SH_(L))        are encoded on the SLM, where the complex values of the lens        sub-hologram are determined using the formula        z_(L)=exp{−i*[(π/λf)*(x²+y²)]} with λ as the        reference-wave-length, f as focal length, and x and y being        orthogonal coordinates in the plane of the sub-hologram.    -   the sub-hologram (S_(P)) of the prism is determined within the        hologram-plane (HE) in order to move the virtual observer window        away from the optic axis.    -   the sub-holograms of the lens and of the prisms are convolved,        which can be represented symbolically as SH=SH_(L)*SH_(P).    -   each sub-hologram (SH) is modulated with a uniformly distributed        phase shift, where the phase shift is different from        sub-hologram to sub-hologram.    -   the sub-holograms are added so as to form the entire hologram.    -   for the representation of computer-generated holograms for        reconstructions which vary in real-time or in quasi real-time.    -   look-up tables are used in the holographic calculation.    -   the object points can be generated at any position within the        reconstruction frustum.    -   the 3D rendering pipeline of graphics sub-systems incorporates        additional processing units for holographic transformation and        encoding.    -   the Z map for the first display wavelength is copied twice for        the second and third display wavelengths.    -   the hologram is calculated for each of the three display        wavelengths in parallel.    -   the colour map RGB contents for two colours are copied to        separate memory sections, so as to ensure independent access to        the three colour components.    -   the lens function and the prism function for each display colour        undergoes a complex multiplication.    -   a random phase is applied for each cluster of the display.    -   the calculated SLM encodings are subjected to subsequent        processing, using additional algorithms in the holographic        display cluster.    -   the holographic calculation can begin before the colour map and        the Z-buffer are available in their entirety.    -   the time required to perform the holographic calculation for        each sub-hologram is less than one frame time period.    -   the time required to perform the holographic calculation for        each sub-hologram is 17 ms or less.    -   used in a military application.    -   each cluster of the display has its own look-up table for        storing the encoding of the sub-holograms which it displays.    -   after having read the content of the SH from the LUT, the        difference between the currently displayed (SH_(n-1)) and the        new SH (SH_(n)) is calculated.    -   the sequential holographic transformation of points in        three-dimensional space, performed by way of extending the 3D        pipeline of graphics cards with a holographic calculation        pipeline, is not restricted to a particular type of SLM.    -   Method of using the holographic display.        G. Hologram Display with Calculation on the Same Substrate, with        Random Addressing of Holographic Displays

Holographic display in which at least some of the calculations performedto determine the encoding of a spatial light modulator are performedusing circuitry which is on the same substrate as the pixels of thespatial light modulator, such that the real space image data which isused in the holographic calculation is the difference between successivereal space image frames, and the holographic display data is sent to theholographic display cluster in the form of sub-hologram difference dataand display memory location data.

-   -   the sequential holographic transformation of points in        three-dimensional space is performed by way of extending the 3D        pipeline of graphics cards with a holographic calculation        pipeline.    -   the holographic calculations are performed using circuitry which        is in between the pixels of the display.    -   the holographic calculations are performed using circuitry which        is outside the pixel matrix, but on the same substrate as the        display.    -   at least some of the calculations performed to determine the        encoding of a spatial light modulator are performed using        circuitry which is on the same substrate as the pixels of the        spatial light modulator, and where the calculations do not        involve the calculation of a Fourier transform or of a Fresnel        transform per se.    -   the calculations are performed in discrete areas of the display,        to encode the pixels of the corresponding discrete areas, on a        discrete area by discrete area basis.    -   the circuitry includes thin film transistors.    -   the video frame rate is at least about 25 Hz.    -   only real space image data is transmitted to the display.    -   the image data consists of intensity and depth map data.    -   the holographic calculation is performed in real time or in        quasi real time.    -   the holographic calculation is performed using a look-up table        approach.    -   sub-holograms are displayed.    -   the holographic computation is spread homogeneously over the        whole display surface.    -   the holographic computation is split into small identical parts        called clusters tiled over the display surface.    -   the holographic display is a high resolution display.    -   a virtual observer window is an eye pupil diameter or more        across.    -   monochrome images are displayed.    -   colour images are displayed.    -   in order to calculate the value of a pixel of the hologram, only        values of a sub-section of the original image are considered.    -   the light used for the reconstruction is not fully coherent        across the entire display, but rather coherence exists within        sub-sections of the display.    -   the holographic transformation is a one dimensional        transformation.    -   the holographic transformation is a two dimensional        transformation.    -   redundant circuitry, such as TFTs, may be manufactured in the        space of the pixel matrix so that such circuitry can be used to        replace some of the circuitry used at device start up, if some        of the circuitry used at device start up is found to have        failed.    -   the wavefront which would be emitted by the object is        reconstructed in one or multiple virtual observer windows (VOW)        and where the reconstruction of each single object point (OP) of        a three-dimensional scene (3D S) only requires a sub-hologram        (SH) as a subset of the entire hologram (HΣSLM) to be encoded on        the SLM.    -   after a discretization of the scene (3D S) to multiple        object-points (OP), for each visible object-point (OP) of the        3D-scene, the complex values of the lens sub-hologram (SH_(L))        are encoded on the SLM, where the complex values of the lens        sub-hologram are determined using the formula        z_(L)=exp{−i*[(π/λf)*(x²+y²)]} with λ as the        reference-wave-length, f as focal length, and x and y being        orthogonal coordinates in the plane of the sub-hologram.    -   the sub-hologram (SH_(P)) of the prism is determined within the        hologram-plane (HE) in order to move the virtual observer window        away from the optic axis.    -   the sub-holograms of the lens and of the prisms are convolved,        which can be represented symbolically as SH=SH_(L)*SH_(P).    -   each sub-hologram (SH) is modulated with a uniformly distributed        phase shift, where the phase shift is different from        sub-hologram to sub-hologram.    -   the sub-holograms are added so as to form the entire hologram.    -   for the representation of computer-generated holograms for        reconstructions which vary in real-time or in quasi real-time.    -   the object points can be generated at any position within the        reconstruction frustum.    -   the 3D rendering pipeline of graphics sub-systems incorporates        additional processing units for holographic transformation and        encoding.    -   the Z map for the first display wavelength is copied twice for        the second and third display wavelengths.    -   the hologram is calculated for each of the three display        wavelengths in parallel.    -   the colour map RGB contents for two colours are copied to        separate memory sections, so as to ensure independent access to        the three colour components.    -   the lens function and the prism function for each display colour        undergoes a complex multiplication.    -   a random phase is applied for each cluster of the display.    -   the calculated SLM encodings are subjected to subsequent        processing, using additional algorithms in the holographic        display cluster.    -   used in a military application.    -   image difference data is received by the holographic calculation        units.    -   if there is no difference, or negligible difference, between        display data for successive frames at a given cluster, then no        data need be sent to the cluster.    -   each holographic calculation unit is sent 3D difference point        image data which are relevant to the reconstruction point or        points it is serves to encode on the SLM.    -   within each holographic display cluster, there is a splitter,        which splits the calculated hologram display data into        sub-hologram data and size and position information, where the        two latter values may be used to compute the address range of        the sub-hologram in the RAM, so that the data of the        sub-hologram SH or SH_(D) are written to the correct SLM cells        within the cluster.    -   a special random access memory (RAM) is used where only the new        SH or SH_(D)s are written on the input side while on the output        side the entire memory is read line by line and the information        is written to the SLM.    -   Method of using the holographic display.        H. Display with Computational Function in the Pixel Space

A display in which computational functions are performed by circuitrywhich is disposed on the same substrate as the pixels of the display.

-   -   computational functions are performed by circuitry which is in        between the pixels of the display.    -   computational functions are performed by circuitry which is        outside the pixel matrix, but on the same substrate as the        display.    -   the delay in displaying data on the display is less than if        computational functions performed by circuitry which is disposed        on the same substrate as the pixels of the display were        performed elsewhere.    -   the computations are graphical computations.    -   is part of a high speed gaming device.    -   is used in military applications.    -   the calculations are performed in discrete areas of the display,        to encode the pixels of the corresponding discrete areas, on a        discrete area by discrete area basis.    -   the circuitry includes thin film transistors.    -   the active regions of at least some of the circuitry consists of        polycrystalline Si.    -   the active regions of at least some of the circuitry consists of        continuous grain Si.    -   the active regions of at least some of the circuitry consists of        polycrystalline SiGe.    -   the active regions of at least some of the circuitry consists of        monocrystalline Si.    -   the image data frame rate is at least about 25 Hz.    -   the computation, which may be a parallel computation, is split        into small identical parts called clusters tiled over the        display surface.    -   the display can be built up through tiling identical clusters        together.    -   the display is a high resolution display.    -   the display is a very high resolution display.    -   colour images are displayed.    -   the colour images displayed are in RGB format.    -   the display is fabricated using liquid crystal on silicon        technology.    -   an additional logic for local forwarding of calculated data        exists, and the additional logic can also be co-used for        forwarding the original image to the clusters, so that at least        some global row and column wires may be eliminated.    -   Method of using the display        I. Occlusion

Holographic display in which at least some of the calculations performedto determine the encoding of a spatial light modulator are performedusing circuitry which is on the same substrate as the pixels of thespatial light modulator, and for which it is ensured that object pointscloser to the virtual observer window mask object points further awayfrom the virtual observer window, along the same line of sight.

-   -   the calculations do not involve the calculation of a Fourier        transform or of a Fresnel transform per se.    -   the hologram encoding data is calculated outside the space        occupied by the pixel matrix, the hologram encoding data is then        compressed using known data compression techniques, and is then        transmitted to circuitry on the display substrate, the circuitry        then performing the function of decompressing the data which has        been received.    -   the 3D rendering pipeline of graphics sub-systems incorporates        additional processing units for holographic transformation and        encoding.    -   sequential holographic transformation of points in        three-dimensional space is performed by way of extending the 3D        pipeline of graphics cards with a holographic calculation        pipeline.    -   the real space image data which is used in the holographic        calculation is the difference between successive real space        image frames, and the holographic display data is sent to the        holographic display cluster in the form of sub-hologram        difference data and display memory location data.    -   occlusion is implemented using calculations which are performed        by circuitry which is present on the same substrate as the pixel        matrix.    -   occlusion is implemented using calculations which are performed        by circuitry which is present in between the pixels of the        display.    -   a virtual observer window is an eye pupil diameter or more        across.    -   the VOW is separated into two or more segments.    -   each VOW segment is about the same size as the human eye pupil        size.    -   each VOW segment is encoded by a different sub-hologram.    -   occlusion is performed at the stage that the depth map and        intensity map are constructed.    -   Method of using the holographic display.        J. Graphics Card Functionalities

Holographic display in which at least some of the calculations performedto determine the encoding of a spatial light modulator are performedusing circuitry which is on the same substrate as the pixels of thespatial light modulator, and in which graphics card functionalities areimplemented using circuitry on the same substrate as the pixels of thedisplay.

-   -   the calculations do not involve the calculation of a Fourier        transform or of a Fresnel transform per se.    -   the hologram encoding data is calculated outside the space        occupied by the pixel matrix, the hologram encoding data is then        compressed using known data compression techniques, and is then        transmitted to circuitry on the display substrate, the circuitry        then performing the function of decompressing the data which has        been received.    -   the 3D rendering pipeline of graphics sub-systems incorporates        additional processing units for holographic transformation and        encoding.    -   sequential holographic transformation of points in        three-dimensional space is performed by way of extending the 3D        pipeline of graphics cards with a holographic calculation        pipeline.    -   the real space image data which is used in the holographic        calculation is the difference between successive real space        image frames, and the holographic display data is sent to the        holographic display cluster in the form of sub-hologram        difference data and display memory location data.    -   graphics card functionalities are implemented using circuitry in        between the pixels of the display.    -   graphics card functionalities are implemented using circuitry        which is outside the pixel matrix.    -   graphics card functionalities include texture mapping.    -   graphics card functionalities include rendering polygons.    -   graphics card functionalities include translating vertices into        different coordinate systems.    -   graphics card functionalities include programmable shaders.    -   graphics card functionalities include oversampling and        interpolation techniques to reduce aliasing.    -   graphics card functionalities include very high-precision color        spaces.    -   graphics card functionalities include 2D acceleration        calculation capabilities.    -   graphics card functionalities include frame buffer capabilities.    -   graphics card functionalities include Moving Picture Experts        Group (MPEG) primitives.    -   graphics card functionalities include performing computations        involving matrix and vector operations.    -   graphics card functionalities include using a 3D-rendering        pipeline which is implemented by TFTs on the same substrate as        the pixel matrix.    -   Method of using the holographic display.        K. 2D-3D conversion

Holographic display in which at least some of the calculations performedto determine the encoding of a spatial light modulator are performedusing circuitry which is on the same substrate as the pixels of thespatial light modulator, and in which 2D-3D image conversion isimplemented.

-   -   the calculations do not involve the calculation of a Fourier        transform or of a Fresnel transform per se.    -   the hologram encoding data is calculated outside the space        occupied by the pixel matrix, the hologram encoding data is then        compressed using known data compression techniques, and is then        transmitted to circuitry on the display substrate, the circuitry        then performing the function of decompressing the data which has        been received.    -   the 3D rendering pipeline of graphics sub-systems incorporates        additional processing units for holographic transformation and        encoding.    -   sequential holographic transformation of points in        three-dimensional space is performed by way of extending the 3D        pipeline of graphics cards with a holographic calculation        pipeline.    -   the real space image data which is used in the holographic        calculation is the difference between successive real space        image frames, and the holographic display data is sent to the        holographic display cluster in the form of sub-hologram        difference data and display memory location data.    -   2D-3D image conversion is implemented using circuitry on the        same substrate as the pixels of the display.    -   2D-3D image conversion is implemented using circuitry not on the        same substrate as the pixels of the display.    -   2D-3D image conversion is implemented using circuitry in between        the pixels of the display.    -   2D-3D image conversion is implemented using circuitry which is        outside the pixel matrix but on the same substrate as the pixels        of the display.    -   2D-3D image conversion is implemented using pairs of        stereoscopic images.    -   the display device calculates a two dimensional (2D) image, with        its corresponding depth map, from the data received.    -   the circuitry which performs the 2D-3D conversion has access to        a library containing a set of known 3D shapes.    -   the circuitry which performs the 2D-3D conversion has access to        a library containing a set of known 2D profiles to which it may        try to match incoming 2D image data.    -   2D-3D image conversion is performed based on a single,        non-autostereoscopic 2D image.    -   Method of using the holographic display.        L. Conferencing (3D Skype™)

Holographic display with which voice and holographic image over internetprotocol (VHIOIP) services are provided.

-   -   at least some of the calculations performed to determine the        encoding of a spatial light modulator are performed using        circuitry which is on the same substrate as the pixels of the        spatial light modulator.    -   the calculations do not involve the calculation of a Fourier        transform or of a Fresnel transform per se.    -   the hologram encoding data is calculated outside the space        occupied by the pixel matrix, the hologram encoding data is then        compressed using known data compression techniques, and is then        transmitted to circuitry on the display substrate, the circuitry        then performing the function of decompressing the data which has        been received.    -   the 3D rendering pipeline of graphics sub-systems incorporates        additional processing units for holographic transformation and        encoding.    -   sequential holographic transformation of points in        three-dimensional space is performed by way of extending the 3D        pipeline of graphics cards with a holographic calculation        pipeline.    -   the real space image data which is used in the holographic        calculation is the difference between successive real space        image frames, and the holographic display data is sent to the        holographic display cluster in the form of sub-hologram        difference data and display memory location data.    -   VHIOIP peer-to-peer communications are provided.    -   file sharing is provided.    -   instant messaging services over a global network to which it is        connected are provided.    -   communication services are provided over a computer network to        which it is connected.    -   file sharing services are provided over a computer network to        which it is connected.    -   instant messaging services are provided over a computer network        to which it is connected.    -   there is provided temporary use of online, non-downloadable        computer software that allows subscribers to utilize VHIOIP        communication services.    -   there is provided online software for downloading that allows        subscribers to utilize VHIOIP communication services.    -   there is provided access to domains and domain database systems        for access to holographic display data.    -   Method of using the holographic display.        M. Encoding Compensations.

Holographic display device in which compensation is applied to theholographic image data at or before the encoding step, to provide animage which is easier to view.

-   -   at least some of the calculations performed to determine the        encoding of a spatial light modulator are performed using        circuitry which is on the same substrate as the pixels of the        spatial light modulator.    -   the calculations do not involve the calculation of a Fourier        transform or of a Fresnel transform per se.    -   the hologram encoding data is calculated outside the space        occupied by the pixel matrix, the hologram encoding data is then        compressed using known data compression techniques, and is then        transmitted to circuitry on the display substrate, the circuitry        then performing the function of decompressing the data which has        been received.    -   the 3D rendering pipeline of graphics sub-systems incorporates        additional processing units for holographic transformation and        encoding.    -   sequential holographic transformation of points in        three-dimensional space is performed by way of extending the 3D        pipeline of graphics cards with a holographic calculation        pipeline.    -   the real space image data which is used in the holographic        calculation is the difference between successive real space        image frames, and the holographic display data is sent to the        holographic display cluster in the form of sub-hologram        difference data and display memory location data.    -   compensation is applied using circuitry on the same substrate as        the pixels of the display.    -   compensation is applied using circuitry in between the pixels of        the display.    -   compensation is applied to the holographic image data at the        encoding step.    -   compensation is applied to the holographic image data before the        encoding step.    -   compensation is applied to correct a scene that is predominantly        light tones and will tend to be underexposed.    -   compensation is applied to correct a scene that is predominantly        dark tones and will tend to be overexposed.    -   Method of using the holographic display.        N. Eye Tracking

Holographic display in which at least some of the calculations performedto determine the encoding of a spatial light modulator are performedusing circuitry which is on the same substrate as the pixels of thespatial light modulator, and in which eye tracking is implemented.

-   -   the calculations do not involve the calculation of a Fourier        transform or of a Fresnel transform per se.    -   the hologram encoding data is calculated outside the space        occupied by the pixel matrix, the hologram encoding data is then        compressed using known data compression techniques, and is then        transmitted to circuitry on the display substrate, the circuitry        then performing the function of decompressing the data which has        been received.    -   the 3D rendering pipeline of graphics sub-systems incorporates        additional processing units for holographic transformation and        encoding.    -   sequential holographic transformation of points in        three-dimensional space is performed by way of extending the 3D        pipeline of graphics cards with a holographic calculation        pipeline.    -   the real space image data which is used in the holographic        calculation is the difference between successive real space        image frames, and the holographic display data is sent to the        holographic display cluster in the form of sub-hologram        difference data and display memory location data.    -   eye tracking is implemented for a single viewer.    -   eye tracking is implemented for multiple viewers.    -   eye tracking is implemented by limiting the search range by        detecting the user's face, then limiting the tracking range by        detecting the eyes, then by tracking the eyes.    -   the eye tracking calculation module for performing the eye        position identification function is provided with a stereo image        pair as supplied by a stereo camera.    -   the module returns the x-, y-, and z-coordinates of each eye        relative to a fixed point.    -   the computation required in order to perform the tracking is        performed by circuitry on the same substrate as the display        pixels.    -   the computation required in order to perform the tracking is        performed by circuitry within the pixel matrix.    -   the holographic encoding on the SLM panel may be displaced in        the plane of the panel.    -   the tracking of eyes in one lateral direction is carried out by        displacing the entire holographic encoding content on the SLM in        the x- or y-direction.    -   tracking is carried out such that the light sources that        coherently illuminate the SLM are moved in synchronism with        position changes of the viewer.    -   Method of using the holographic display.        O. Aberration Correction

Holographic display in which at least some of the calculations performedto determine the encoding of a spatial light modulator are performedusing circuitry which is on the same substrate as the pixels of thespatial light modulator, and in which aberration correction isimplemented.

-   -   the calculations do not involve the calculation of a Fourier        transform or of a Fresnel transform per se.    -   the hologram encoding data is calculated outside the space        occupied by the pixel matrix, the hologram encoding data is then        compressed using known data compression techniques, and is then        transmitted to circuitry on the display substrate, the circuitry        then performing the function of decompressing the data which has        been received.    -   the 3D rendering pipeline of graphics sub-systems incorporates        additional processing units for holographic transformation and        encoding.    -   sequential holographic transformation of points in        three-dimensional space is performed by way of extending the 3D        pipeline of graphics cards with a holographic calculation        pipeline.    -   the real space image data which is used in the holographic        calculation is the difference between successive real space        image frames, and the holographic display data is sent to the        holographic display cluster in the form of sub-hologram        difference data and display memory location data.    -   aberration correction is implemented using circuitry which is on        the same substrate as the pixel matrix.    -   aberration correction is implemented using circuitry which is in        between the pixels.    -   aberrations are corrected dynamically through the encoding of        the spatial light modulator.    -   corrected aberrations are those in the lenses in a lenticular        array.    -   corrected aberrations are those in the lenses in a 2D lens        array.    -   sub-holograms are displayed.    -   a sum-hologram is generated from the sub-holograms.    -   the aberration correction algorithm is performed in parallel,        and independently, of the holographic calculation up to the step        where the sum-hologram is generated.    -   the sum-hologram and the aberration correction map are modulated        together.    -   the aberration correction algorithms are implemented        analytically.    -   the aberration correction algorithms are implemented using        look-up tables (LUT).    -   Method of using the holographic display.        P. Speckle Correction

Holographic display in which at least some of the calculations performedto determine the encoding of a spatial light modulator are performedusing circuitry which is on the same substrate as the pixels of thespatial light modulator, and in which speckle correction is implemented.

-   -   the calculations do not involve the calculation of a Fourier        transform or of a Fresnel transform per se.    -   the hologram encoding data is calculated outside the space        occupied by the pixel matrix, the hologram encoding data is then        compressed using known data compression techniques, and is then        transmitted to circuitry on the display substrate, the circuitry        then performing the function of decompressing the data which has        been received.    -   the 3D rendering pipeline of graphics sub-systems incorporates        additional processing units for holographic transformation and        encoding.    -   sequential holographic transformation of points in        three-dimensional space is performed by way of extending the 3D        pipeline of graphics cards with a holographic calculation        pipeline.    -   the real space image data which is used in the holographic        calculation is the difference between successive real space        image frames, and the holographic display data is sent to the        holographic display cluster in the form of sub-hologram        difference data and display memory location data.    -   speckle correction is implemented using circuitry which is on        the same substrate as the pixel matrix.    -   speckle correction is implemented using circuitry which is in        between the pixels.    -   speckle is corrected dynamically through the encoding of the        spatial light modulator.    -   sub-holograms are displayed.    -   a sum-hologram is generated from the sub-holograms.    -   the speckle correction algorithm is performed in parallel, and        independently, of the holographic calculation up to the step        where the sum-hologram is generated.    -   sum-hologram and the speckle correction map are modulated        together.    -   the speckle correction algorithms are implemented analytically.    -   the speckle correction algorithms are implemented using look-up        tables (LUT).    -   Method of using the holographic display.        Q. Decryption in Digital Rights Management (DRM) for a        Holographic Display

Holographic display device in which decryption and hologram calculationare executed using circuitry which is on the substrate of the pixelmatrix.

-   -   decryption and hologram calculation are executed in a        distributed sense using circuitry which is distributed across        the substrate of the pixel matrix.    -   decryption and hologram calculation are executed using circuitry        which is within the pixel matrix.    -   decryption and hologram calculation are executed using circuitry        which is outside the pixel matrix, but on the same substrate as        the pixel matrix.    -   there is no single place on the substrate from which all        decrypted data can be captured.    -   different decryption keys are used for different areas of the        panel.    -   Method of using the holographic display.        R. Decryption in Digital Rights Management (DRM) for a 2D        Display

2D display device in which decryption calculations are executed in adistributed sense using circuitry which is distributed across thesubstrate of the pixel matrix.

-   -   decryption calculations are executed in a distributed sense        using circuitry which is within the pixel matrix.    -   decryption calculations are executed in a distributed sense        using circuitry which is outside the pixel matrix, but on the        same substrate as the pixel matrix.    -   there is no single place on the substrate from which all        decrypted data can be captured.    -   different decryption keys are used for different areas of the        substrate.    -   Method of using the display.

2D display device in which decryption calculations are executed usingcircuitry which is in a single area of the display substrate.

-   -   the circuitry is inside the pixel matrix.    -   the circuitry is outside the pixel matrix.    -   Method of using the display.        S. Software Application Implemented in Hardware, Hard-Wired into        a Display

Display device in which an application which may be implemented usingsoftware is instead implemented in hardware using circuitry which isdistributed across the substrate of an SLM panel.

-   -   the display is a 2D display.    -   the display is a holographic display.    -   the application is implemented using circuitry which is in        between the pixels of the display.    -   the application is implemented using circuitry which is in        outside the pixel matrix of the display.    -   Method of using the display.        T. Variable Beam Deflection with Microsprisms

Holographic display with which the viewer or viewers are tracked using amicroprism array which enables controllable deflection of optical beams.

-   -   two dimensional deflection is obtained by using two microprism        arrays in series.    -   the prisms are Micro Liquid Prisms.    -   the optical effect of lens aberration can be reduced.    -   the VOWs are placed at the viewer's or viewers' eyes.    -   a focussing means placed before or after the prism array will        assist to converge the light rays into the VOW.    -   the prisms do not all have the same deflection angle.    -   the prisms do not all have the same deflection angle such that        the light rays exiting the prism array converge somewhat at the        VOW.    -   the prism angle calculation is performed in computational        circuitry on the SLM's substrate.    -   the prism angle calculation is performed in computational        circuitry placed on the substrate of the prism array.    -   the substrate of the SLM is also used as the substrate for the        prism array.    -   a phase correction is applied to compensate for phase        discontinuities introduced by the prism array.    -   the phase correction is performed by the SLM.    -   the holographic image is generated in a projection-type        apparatus, where the projection involves imaging a SLM onto the        prism array while the reconstruction of the desired 3D scene        occurs in front of the VOW.    -   phase compensation for the prism array is provided when imaging        the SLM onto the prism array.    -   phase compensation for the prism array is provided by an        additional SLM placed near to the prism array.    -   the SLM is transmissive with the prism array reflective.    -   the SLM is reflective with the prism array transmissive.    -   Method of using the holographic display.

1. A holographic display including a spatial light modulator, andincluding a position detection and tracking system, such that a viewer'seye positions are tracked, with variable beam deflection to the viewer'seye positions being performed using a microprism array which enablescontrollable deflection of optical beams, in which a phase correction isapplied to compensate for phase discontinuities introduced by the prismarray in order to compensate for different optical path lengths to theviewer's eye positions.
 2. Holographic display of claim 1, in which thevariable beam deflection is continuously variable.
 3. Holographicdisplay of claim 1, in which the variable beam deflection is performedusing electrowetting technology.
 4. Holographic display of claim 1, inwhich the variable beam deflection is performed using variable voltagedifferences applied to different electrodes located on different sidesof each of an array of electrowetting cells.
 5. Holographic display ofclaim 1, in which the microprism array comprises a plurality of prisms,such a prism being an electrowetting cell, each electrowetting cellhaving at least two electrodes each coated with a hydrophobic insulatorand an interface between a transparent conducting liquid and anotherfluid, a contact angle of the interface being formable as a function ofa voltage difference applied to at least one of the electrodes withrespect to the transparent conducting liquid.
 6. Holographic display ofclaim 1, in which two dimensional deflection is obtained by using twomicroprism arrays in series.
 7. Holographic display of claim 1, furthercomprising a point light source or a line light source and a lens forfocusing light, wherein a virtual observer window is placed at viewer'sor viewers' eyes, the virtual observer window being generated at aFourier plane of the spatial light modulator, the virtual observerwindow comprising a size which is not exceeding a periodicity intervalof one diffraction order of the spatial light modulator (SLM). 8.Holographic display of claim 7, in which a focussing means placed beforeor after the prism array assists to converge light rays into the virtualobserver window.
 9. Holographic display of claim 1, in which an opticaleffect of lens aberration are reducible by correcting dynamicallythrough encoding of the spatial light modulator.
 10. Holographic displayof claim 1, in which prisms of the prism array are controlledindependently from each other and therefore each controlled prismestablishes a beam deflection depending on the control of eachcontrolled prism.
 11. Holographic display of claim 1, further comprisinga point light source or a line light source and a lens for focusinglight, wherein a virtual observer window is placed at viewer's orviewers' eyes, the virtual observer window being generated at a Fourierplane of the spatial light modulator, the virtual observer windowcomprising a size which is not exceeding a periodicity interval of onediffraction order of the spatial light modulator, in which a focussingmeans placed before or after the prism array assists to converge lightrays into the virtual observer window, in which prisms of the prismarray are controlled independently from each other and therefore eachcontrolled prism establishes a beam deflection depending on the controlof each controlled prism and in which the prisms do not all have a samedeflection angle such that light rays exiting the prism array convergesomewhat at the virtual observer window.
 12. Holographic display ofclaim 1, in which a prism angle calculation is performed incomputational circuitry on a substrate of the spatial light modulator orin which a prism angle calculation is performed in computationalcircuitry situated on a substrate of the prism array.
 13. Holographicdisplay of claim 1, in which the spatial light modulator's substrate isalso used as the prism array's substrate.
 14. Holographic display ofclaim 1, wherein the spatial light modulator is adapted to be capable ofchanging phase of light interacting with the spatial light modulator andin which the phase correction is performed by operation of the spatiallight modulator.
 15. Holographic display of claim 1, in which aholographic image is generated in a projection-type apparatus, where theprojection involves imaging the spatial light modulator onto the prismarray while a reconstruction of a desired 3D scene occurs in front ofthe virtual observer window.
 16. Holographic display of claim 1, inwhich phase compensation for the prism array is provided when imagingthe spatial light modulator onto the prism array.
 17. Holographicdisplay of claim 1, in which phase compensation for the prism array isprovided by an additional spatial light modulator placed near to theprism array.
 18. Holographic display of claim 1, in which the spatiallight modulator is transmissive with the prism array reflective ortransmissive.
 19. Holographic display of claim 1, in which the spatiallight modulator is reflective with the prism array transmissive.
 20. Amethod of generating a holographic reconstruction of a three dimensionalscene, made up of multiple discrete points, using the holographicdisplay of any previous claim, the display including a light source andan optical system to illuminate the spatial light modulator; comprisingthe step of: encoding a hologram on the spatial light modulator.